In this article, we will discuss oxygen sensors, what they do and how to test oxygen sensors. I will try to explain a little about them and answer a few questions. Keep in mind that this article is not vehicle specific, but applies to all cars in general. As always, if you are in doubt about something, consult your owner’s manual or repair guide for vehicle specific information.

When should I replace the oxygen sensor?

Usually, oxygen sensors require replacement around 60 to 100K miles. You should check the owner’s manual or repair guide for the recommended mileage for your car. Most modern cars have a service light or gauge that lights up when the preset mileage has been reached. This light is usually triggered by a few different things, such as a mechanical mileage counter or by counting a certain amount of turns of the key in the ignition. In these cases, the light is merely a reminder to service the sensor. Be sure not to confuse a service reminder light with an actually failure light. A failure light is a light that only illuminates when the sensor actually fails. Check the owner’s manual or repair guide if you are in any doubt as to whether or not the light is a failure light or service light. It is not always necessary to replace the sensor at the factory recommended mileage however. These are usually just a service recommendation. Naturally, parts do wear out and fail over time, so it’s always a good idea to practice preventative maintenance on your car.

What are the symptoms of a bad oxygen sensor?

The biggest indicator of a faulty oxygen sensor is a noticeable decrease in fuel economy, along with a rich mixture. Now, this does not automatically indicate that the sensor has failed. Be sure to check all vacuum hoses for leaks as well as the ignition system, check the plugs, (are they fouled?) check the rotor, distributor cap, points, spark plug leads, and condenser (check all of these where applicable) Vacuum leaks and ignition problems are notorious for causing fuel economy problems. It’s a good idea to inspect and re-new the vacuum hoses every couple of years anyway. Other symptoms of a faulty sensor are a loss of power, (particularly when accelerating from a stand-still), overheating, and spark plug fouling, both of these are due to an increased rich or lean running condition.

Most modern cars nowadays come with sort of a built in troubleshooting guide that can help you diagnose if the sensor is bad. There is usually a port or connector where you can plug in a computer and extract codes from the fuel injection computer. In the case of most new cars, when an error occurs, it generates a code and stores it. Using the computer, you can extract the code from the fuel injection computer. This is invaluable in determining not only a bad oxygen sensor, but all sorts of other problems as well. In many cases, this can tell you if the sensor is bad, however if it does not, keep reading, the steps below will go over how to test the sensor.

What can damage the oxygen sensor?

Sometimes, but not always, certain home or shop repairs can possibly damage an oxygen sensor. Usually, the sensor is placed in the exhaust manifold very near the bottom of the engine. It is in this area that you have components such as oil pans, valve covers, and other panels and covers that are usually sealed with a silicone-based sealer such as RTV. Some of these sealers contain fumes that will damage the sensor. If you are working in the area of the sensor, be sure to use a silicone-based sealer that is labeled “Oxygen Sensor Safe” You can find this sealer at any auto parts store. Other things that can destroy a sensor are anti-freeze/coolant, using leaded fuel (even though it is hard to find these days), as well as a sustained rich running engine. (This is usually the case when the oxygen sensor fails) When the engine is running rich for an extended amount of time, carbon will begin to build up on the inlets for the sensor, clog it, and eventually burn it out.

Is it safe to test an oxygen sensor?

As long as you are merely testing the voltage output, it is usually safe to test the sensor. You do not want to apply any sort of voltage to the sensor, this can fry the sensor. Also, you do not want to check resistance between terminals as checking resistance means that you are sending voltage into a circuit, and measuring the amount returning. This can fry the sensor as well.

How does this thing work?

Oxygen sensors are essentially chemical generators. They work by constantly measuring the oxygen content inside the exhaust manifold and comparing it to the air outside the engine. If this comparison shows little or no oxygen in the exhaust manifold, a voltage is generated. This voltage is then sent to the fuel injection computer, where it is received and based on the voltage, the fuel injection computer makes the necessary adjustments to change the overall fuel-air mixture of the engine. When the oxygen sensor measures the correct mixture, the voltage drops and it sends the appropriate signal to the computer to stop adjusting the mixture. This is a non-stop exchange of signals between the sensor and the computer, and it is constantly making adjustments depending on the needs of the engine. When the sensor fails, it stops sending voltage to the fuel injection computer, and usually the computer interprets this as “ok, we aren’t getting a signal, so we better enrich this engine as much as we can”, hence a rich running engine.

Oxygen sensors usually put out a very small voltage when measuring oxygen content. Typically, they only put out from 0 to 1.1 volts max.

All internal combustion engines need a proper air-fuel ratio in order to run correctly. Gasoline engines need to run a ratio of 14.7 parts of air to one part of fuel. (Air cooled motors typically need to be slightly richer).

When an engine has more fuel than it needs, all the oxygen in the cylinder head is consumed and the resulting exhaust gases contain almost no oxygen. This usually causes the sensor to generate a voltage of greater than 0.45 volts. If the engine is running too lean, all the fuel is burned, and the extra oxygen remaining flows out into the exhaust manifold. The oxygen sensor detects the extra oxygen and the voltage signal will drop to below 0.45 volts.. 0.45 volts is usually the voltage where the car is neither running rich nor lean, this is when the car’s mixture is usually perfect.

Oxygen sensors usually generate an output voltage between 0.2 to 0.7 volts. However, Oxygen sensors doe not begin to generate full output voltage until it reaches about 600 degrees F. Some oxygen sensors have a built-in heating element that lets the sensor heat up quicker. Keep in mind that most oxygen sensors work in an open loop until they have reached a certain temperature. What this means is that until it has heated up, the car will not use the oxygen sensor to measure the mixture, but rather use all the other sensors on the car. The sensor will generate a constant 0.45 volts until it has heated up. Once the sensor reaches a certain temperature, it becomes a closed loop and the sensor starts to generate variable voltage.

How do I test the sensor?

The first step is to let the car warm up to operating temperature. You will need a high-impedance DC voltmeter to measure the output voltage. It’s a good idea to use a high quality or digital voltmeter. Analog voltmeters usually are not sensitive enough to register the small voltages generated by the oxygen sensor.

The first step is to get the engine warmed up to operating temperature. This insures that the oxygen sensor will generate voltage. Now, attach the positive lead of the voltmeter to the oxygen sensor output wire.

This wire should remain connected to the harness going to the computer, so you may find it necessary to use a jumper or trim back the insulation so you can attach the leads. Connect the negative lead to a good engine ground, such as the engine block, or any bare metal on the vehicle’s chassis. Now, set the voltmeter to look for 1 volt DC. When you turn the key on, do not start the engine. You should see a change in voltage on the meter in most late model cars. If not, check the connections.

Now start the engine. In the case of single wire sensors, you should run the engine above 2000 rpm for a few minutes to heat up the O2 sensor and try to get into closed loop. The sensor showing several cross counts per second indicates closed loop operation. It may help to rev the engine between idle and about 3000 rpm several times. The computer will recognize the sensor as hot and active once there are several cross counts.

You are looking for voltage to go above and below 0.45 volts. If you see less than 0.2 and more than 0.7 volts and the value changes rapidly, you are through, your sensor is good. If not, is it steady high, near 0.45 or steady low? If the voltage is near the middle, you may not be hot yet. Run the engine above 2000 rpm again. If the voltage is steady high, create a vacuum leak. Try pulling the PCV valve out of its hose or remove the oil filler cap and letting air enter. You can also use the power brake vacuum supply hose. If this drives the voltage to 0.2 to 0.3 or less and you can control it at will by opening and closing the vacuum leak, the sensor is usually good. If you are not able to make a change either way, stop the engine, unhook the sensor wire from the computer harness, and reattach your voltmeter to the sensor output wire. Repeat the rich and lean steps. If you can't get the sensor voltage to change, and you have a good sensor and ground connection, try heating it once more. Repeat the rich and lean steps. If still no voltage or fixed voltage, you have a bad sensor. If you are not getting a voltage and the car has been running rich lately, the sensor may be carbon fouled. It is sometimes possible to clean a sensor in the car. Do this by unplugging the sensor harness, warming up the engine, and creating a lean condition at about 2000 rpm for 1 or 2 minutes. Create a big enough vacuum leak so that the engine begins to slow down. The extra heat will clean it off if possible. If not, the sensor is fried. In either case, fix the cause of the rich mixture and retest. If you don't, the new sensor will fail.

My car has two (or more) wires coming out of the sensor, which wire is the signal output?

Most modern cars used a heated oxygen sensor. In this case, there will be two three or four wires instead of one. What the heating element does is heat the oxygen sensor up quicker than simply relying on the heat of the exhaust manifold.

If you have two, three, or four wires, use a 15 or higher volt scale on the meter to test each wire for 12 volts. You will need to determine which wire is the signal output wire. Once you have determined which wire is the output signal wire, test the sensor as shown above.

A heated oxygen sensor with two wires is usually wired like this (pic o2_sensor_diagram_2.jpg) One wire is 12 volts for the heating element. The other wire is the signal output wire to the fuel injection computer. In this case, the oxygen sensor casing is the ground.

With a 3 wire oxygen sensor, it is wired like this, (pic o2_sensor_diagram_3.jpg) one wire is 12 volts for the heating element, one is ground for the heating element, and the last wire is the signal output to the fuel injection computer.

Lastly, with a 4-wire oxygen sensor, the output signal works in a constant loop, essentially, the fuel injection computer sends a signal to the sensor, and the sensor then sends the signal back to the computer. This is achieved by having one wire carry the signal to the sensor, and then another wire carries the signal back to the fuel injection computer. You also have a wire carrying 12 volts to the heating element, and the last wire is the ground for the heating element. (pic o2_sensor_diagram_4 jpg) With a 4-wire sensor, you will need to measure the voltage fluctuations between the two signal wires. To do this, start the car and let it warm up. Next, disconnect the oxygen sensor and measure the voltage between the wires. Now take off the oil filler cap to simulate a rich running condition. Watch the voltage, if it begins to fluctuate rapidly, then the sensor is good and you’re done. If it stays the same, it’s probably fried.

Well, there you have it - it's really not too difficult at all. If you would like to see more technical articles like this one, please continue to support Pelican Parts with all your parts needs. If you like what you see here, then please visit our online BMW catalog and help support the collection and creating of new and informative technical articles like this one. Your continued support directly affects the expansion and existence of this site and technical articles like this one. As always, if you have any questions or comments about this helpful article, please drop us a line.

Comments and Suggestions:

Farid	Comments: Hi,I have caprice Ls 89.The previous owner of the car disconnected O2 sensor.After one year of driving I found that the car has no O2 sensor.All these times there was no engine light on and no code.Why it is so?without o2 sensor fuel consumption was 14 lits per 100 km.
May 3, 2013

The Maverick	Comments: Hi Nick, It is wonderful to know that one can do all these technologically advanced searches on an engine to find problems such as O2 lean settings etc. We are however stuck in a small 3rd world African country called Namibia or previously known as South West Africa where such advances in technology are few and far between. One can get them for the more expensive brands such as BMW and Mercedes and all the later models,, but for the old 2001 KIA Sportage with it's antiquated Mazda FE3N engine,, I am not even going to go to any further expense. I will grin and bear it for another few days until the Toyota engine is ready and then some other guy with more patience and money can have the engine to fool around with. The new under hood wiring harness is ready today and the bell housing will be ready on Friday and then all I need are the engine mountings. Then yippee,,, I can go play around in the desert again without fear of running out of power or fuel.. Thanks for your input. It is much appreciated.
April 23, 2013
	Followup from the Pelican Staff: No problem, glad to help. - Nick at Pelican Parts

The Maverick	Comments: Hi Nick,, I have all but given up on the shop which did the original work. They are responsible for the engine overheating and requiring a rebuild in the first place by installing the fan the wrong way around. I have refused to pay them for their original error. We only communicate via our lawyers. I have in the meantime sourced a Toyota 2.4 engine in very good condition and low kilo's and will be preparing this to install in the Kia in the next few weeks. All I need to do is have a bell housing conversion made and then it will read on the spare wheel cover "Reliably powered by Toyota" !! My previous Toyota 2.4 Hilux pickup had over 400 thousand Kilos on the clock before I sold it. It also never let me down and was rather economical on fuel for a 4 x 4 which is more I can say for the Kia !!! No O2 sensors there to give me trouble... Fool me once,, shame on you,,, fool me twice,, shame on me !!
April 23, 2013
	Followup from the Pelican Staff: before you stick the fork in the engine. See if you can put a scanner on it. Check for an o2 hanging lean, or something that could force a rich condition. Good luck! - Nick at Pelican Parts

The Maverick	Comments: I drive a 2001 Kia Sportage 2.0 DOHC 4 x 4 and I am experiencing terrible fuel consumption.. The engine was entirely rebuilt after a bad overheating episode and the airflow sensor as well as the Oxygen Lamda sensor at the manifold were replaced. The car ran fine for one or two days after these replacements but has now reverted back to very heavy fuel consumption... What can be the problem and where can I start looking for problems. All hoses were replaced and the job was professionally done and I am about ready to park it on a deserted road with a full tank and the keys in the ignition in the hope that someone will relieve me of it and its problems !!! It emits a black smoke like a diesel, but after testing all sensors,, everything seems fine and working,,,, yet it continues to bankrupt me with fuel consumption !!! Please send help to maverickmike@iway.na
April 19, 2013
	Followup from the Pelican Staff: If you tested everything and it seems fine, yet vehicle smokes badly, you have missed something. I would return to the shop that installed then engine and ask their advice on the matter. - Nick at Pelican Parts

ada	Comments: i have a e36 1994 can someone help me my exhust emissions it fail it mot i have put on a new lambda the fast idle ane second fast idle test
March 18, 2013
	Followup from the Pelican Staff: What gases failed? Can you share the tailpipe emission readout of all gases? - Nick at Pelican Parts

janelle	Comments: I have a 1996 nercury villager van that when trying to accelerate it goes slow then jerks can u help with what it could be? greatly apperciated.
March 12, 2013
	Followup from the Pelican Staff: Sounds like you have a hesitation. Check the engine control module for fault codes. - Nick at Pelican Parts

evo

Comments: Hi, can anyone help me. I have a 2001 saxo vtr, I have just noticed it has 2 lamba o2 sensors for the ehaust but only 1 is plugged in an the other is rapped up an pushed to the side, this is how I braught It so I don't no if its had a different exhaust fitted wich only allows 1 02 sensor, my engine management light is on an is using quite abit of fuel, what can I do, can I wire them both up into 1 sensor. Thank you

February 13, 2013

ZWolf24	Comments: Hello many, I can't seem to figure out which wires are which and no multimeter, but i hope its an easy once the pic is seen. Outside wires are white, inside right wire black, inside left gray? Just hoping to know which is which if possible. Thank you.
February 1, 2013
	Followup from the Pelican Staff: I'm not sure which car you referring to here. I will copy this question forms and perhaps you can add that information there and we can help you out. - Wayne at Pelican Parts

JohnW	Comments: Hi, I have 2001 e39 with 135000 miles, got SES light on and Peake code shows 19 96 . I change 2 new pre-cat O2 sensors. Reset fault code but still got SES light on after restart engine. Please help
January 3, 2013

kevin

Comments: I have a 03, f-250, get no voltage signal back on my actron scanner for the 2nd bank co2 sensor, I've replaced both co2/heater sensors, replaced the ecu, disconnected the co2 sensor on the 2nd bank from harness and checked with a millivolt meter it operates correctly, when this is disconnected I get no lights on dash board. traced the signal wires back to ecu and they are ok, need help.

December 29, 2012

samc	Comments: My local mechanic thinks my theory is full of hot air. I've had my 98 540i for over six years and had 3 DEQ tests in Oregon. The computer does it's thing and the car passes. The last two times I've done that the check engine soon light comes on within 2 miles of leaving and the problem both times has been an O2 sensor. Am I just randomly unlucky ?
October 24, 2012

jose	Comments: I have a 97 neon and i just replaced the O2 sensors but i am still getting an error code for down stream sensor could that be the catalytic converter, might that be clogged
October 3, 2012

wstone88	Comments: I have a 99 ford town car while runing i ran a water hose into exhaust to check catalytic converter . Now car wont start and i sprayed starting fluid into intake but it wants to start .what could be wrong.
August 27, 2012

Trish	Comments: We have a dodge caravan 2000 that we bought from a tow yard. We have had the vehicle for several years and it has done us really well until.recently. when driving in warmer weather at a higher altitude .about 4000u plus.. it will drop mileage and then shut down. If u unplug the battery and reset the computer sit for about 10 min then rehook will run fine for rest of time driving.. could this be an o2 sensor?
July 10, 2012
	Followup from the Pelican Staff: Unlikely it is the o2 sensor. What may be happening is the vehicle sets a barometric pressure spec when key is turned ON, then you go up in altitude and things get skewed. Cycling the key resets the baro reading and allows to you to drive again. - Nick at Pelican Parts

Gerry

Comments: Great article, thanks, my '89 E34 535i just started running rough after I refuelled. Thinking I had a dose of crook fuel, I quickly replaced the fuel filter. Did not help. Symptoms are, smooth initially, then if throttle depressed any more than about 15%, she starts to miss, buck and finally loose power. Most disconcerting for such a normally silky smooth engine. Fuel consumption has now risen to 26.4 litres/100km, eeeek! 02 sensor hopefully will solve the issue, as I can't justify a smoke generator. Cheers all from Australia, cya.

June 17, 2012

joji

Comments: My Car2001 subaru legacy BH5 needs a couple of cranks to get it started in the morning. Then would need to pump gas several times for it to idle.It needs about 10min idling to get some power on it and runs fine. If not left idle it would not have power even if I step on the gas and max. speed is 15km/h but would run fine after some time. OBD scan threw "P0031 HO2S heater circuit bank1 sensor 1" trouble code. could this be causing this problem? I have replace MAF sensor

May 16, 2012

mikemike

Comments: I have a 99 pontiac firebird 3800 Automatic with 189k miles on it. It ran great when I got it, but here recently it seems like it been missing real bad, so I ran a scan on it from Advance Auto and they told me it was misfiring on two cylinders and something about the EGR vavle. I replace the middle coil pack on it I had to do the same thing on my Camaro because water would drip directly on the coil pack, But that actually fixed the problem.and it seemed to help alot but reving it up from idle it cuts out like it still misfiring. Do you think 2 or 3 coil packs could go bad at the same time and the misfiring will code the computer wrong about the EGR? Thanks

April 5, 2012

22 hornet	Comments: 03 dodge hemi gas mileage has dropped off the smell of gas at the tailpipe and white smoke think it would be the o2 sensors
March 28, 2012

Scott	Comments: The article about oxygen sensors had just the right amount of technical language. It was well written and clear, and I could follow it perfectly. Thank you so much for a very informative and helpful explanation!
March 15, 2012

Limcmeng	Comments: Hi I have been experiencing drop in engine revsmore than usual immediately after a gear change only when the engine is not fully warmed up yet. Can this be the oxygen sensor issue?
March 14, 2012

Thomas

Comments: Oxygen sensors generate absolutely NO voltage when cold. They do not generate a steady .45 volts. That is a voltage produced or derived, since it actually comes from the vehicle's power system within the computer and is fed through a very high resistance to the O2 sensor circuit. This tells the computer that the O2 sensor is not producing its own voltage. Once the O2 sensor is heated up, it will override this voltage. It will both drive the voltage as high as one volt and be able to pull the voltage all the way down to zero volts. If you disconnect the O2 sensor, you will see the .45 volts generated by the computer, which proves that it is not generated by the sensor.

March 6, 2012

woodchip

Comments: My 2008 Impala with 3.5L Flex-Fuel engine got 30 MPG new and after using E85 it dropped to 26 and never came back. One year later it started missing and Chevy said a bad injector, replaced it, still missed, Chevy then said ECU, replaced it and 30 MPG returned. Unknowingly, I used E85 again and MPG dropped and never came back. I now get 27.6 year around. I would like to replace the ECU but Chevy says the Check Engine light has to come on before they would replace the ECU. Could the Oxygen sensor be bad or should I buy the board myself and replace it. Any thoughts would be appreciated.

February 13, 2012

Oldtimer	Comments: I have a 2002 Hyundai Elantra with 56K on it When starting from cold all is okay, after the engine is warm the revs are slow to drop when changing gear. Could this be an oxygen sensor? No errors showing up on dashboard. Many thanks for any help.
January 27, 2012

Sammy

Comments: My girlfriend just bought a 2001 Infiniti I30 with 115,000 miles. Less than a week after purchasing, service engine light came on. Local mechanic said he thought it was automatic warning about one of the oxygen sensors, but no need to replace immediately. Now occasionally getting acceleration hesitation issue, very bad recently when trying to go above 65 mph, wouldn't go any faster? Could new issue be from sensor or some other issue? Other than this problem really like car & have read they are very reliable high mileage vehicles.

January 24, 2012

MTkamper	Comments: Dodge intrepid with 3.5L engines did not have ANY problems' with sludge. The 2.7 is different story. The 3.5 is one of the best motors dodge has come out with. I am still running a 94 Chrysler LHS with 3.5L and rolled 200,000 miles last yr! Still runs great! Been Chrysler & ASE master tech for 15 yrs & if the 3.5 had issues, I'd no bout em
January 23, 2012

warson

Comments: I have an 04 VW Touoareg V6 w/97000 miles. The wrong octane gas 87 was installed, and after approximately 100 miles, the engine lite came on while idling on cold weather. The manual said possibly exhaust problem, but the engine still runs well. It hasn't been checked with an OBD Unit yet. Could the lower octane91 recommended have tripped the sensor? Should I install octane boost? Would the lean octane trip a sensor?

January 20, 2012

rabbitboy	Comments: I have a 2003 chevy implala. It runs good untill a go up a hill. Then it loses power.C ould it be a oxygen sensor or a bad a bad catalysic converter. The check engine light does come on.
January 12, 2012

MoparStevo

Comments: Yo car salesman wanna be-mechanic!! Must be a Ford fan right? Saying 2004 Dodge Intrepids with 3.5 liters are notorious for mechanical and sludge problems and dont make it past 8 years huh? Posted in 2011?!? So you "predict" that a 2004 engine wont make it past 2012 huh? You must be really good!! Ever seen the inside of a FOMOCO engine? 400 pounds of cheap China steel with 150 pounds of sludge and grime holding it together. Same thing with a General Motors engine only instead of grime its 150 pounds of silicone holding that mess together. The best part of you was brown and ran down your mothers leg buddy. Hey Frank I'd start with your coil packs. Heat can cause a bad coil pack to act up. O2 sensors dont usually cause that big of a problem unless theres other factors compounding the problem like a rich fuel/air mixture too. Which is doubtful with dry plugs. Have a nice day everyone!

January 11, 2012

Dolly

Comments: I have a 2002 Mercury Sable premium. It has under 54000 miles. Last week the engine light came on and I took it to get checked. Air flow sensor was changed. I was on the highway last night and started to hear a screeching sound and the engine light was flashing. I got off the nearest exit and had the car towed back home. Now the car starts with no problem but has a rattle sound and the engine light is steady. Waiting to call another tow to bring it to the shop. Of course I won't drive it there which might cause more damage. Any idea what the problem might be? Thanks for any info and have a Good New Year.

December 29, 2011

BMWinSD

Comments: I have a 96 BMW 740iL that is getting error codes 0156, 1186 and 1187. I looked up what those codes mean, and they seem to be due to issues with the post cat O2 sensor. Does this mean that those sensors need to be replaced, or are there other things that can be done to eliminate those codes? I am assuming that those codes are not preventive. They keep coming back after they are erased.

December 21, 2011

Metsada	Comments: I have a new 2011 bmw X3 35i for 3days now. Many people said its fuel consumption about 19-22mpg somehow my car is only 11mpg, is there something wrong with my car?
December 15, 2011

Spookydragon	Comments: Hi, I have a 95 Audi cab 2.6 V6 ABC engine, it has a three wire zirconia sensor on each engine manifold, 2 white heater wires and a black sensor wire, the right bank sensor tested OK but the other one gives me 12 volts on the sensor wire, they're not broke or crossed and there's only one way to connect up, what gives ?
November 30, 2011

nissanguy	Comments: I have a 94 sentra, has been missing while idleing and a plug is not firing. The other day i went to start it and it ran for like 5 seconds and just quit..now it cranks but will not turn over. I pulled the code and it lead me to the O2 sensor..everyone is telling me that the sensor itself will not cause the car to do what it's doing..is that true? thanks.
November 30, 2011

man55	Comments: mercedes ml320 petrol 1999 engine starts first time avery time but will not rev up mote then 2500 rpm if accelarated over that it atart missing and drop the rev to 900rpm and start missing
November 24, 2011

chris

Comments: could a bad sensor make your engine overheat? yes, but only if the engine is badly undercooled to begin with. could a bad sensor make one cylinder misfire? conceivably, but not likely. the fact is a misfiring cylinder will make the sensor read lean no matter what the ecu does, so it will report a bad sensor if it's not too smart. i would test the sensor in a standard rederence cell, look for another cause to the misfiring, and go from there.

November 24, 2011

Jessica

Comments: I've noticed that there haven't been any new responses to the questions asked, but I'm feeling slightly lost so it can't hurt to ask. We have a 99 Pontiac Montana that has started to give me trouble last night. With a "jog" to the motor, I ran it in to be checked out at the nearest garage. After being told that they can't do anything at that point in the day, I was instructed to just take it home. They fiddled with some fuses, poked around under the hood, and hooked it up to a computer that showed a bad O2 sensor and cylinder 2 not firing. Upon leaving, less than half a mile down the road, my temp guage went from the typical reading to being buried in the red. Is it, at all, possible that the O2 sensor is causing all of my issues? Thanks so much in advance to anyone who is able to offer some insight!

November 23, 2011

Fawn

Comments: I have a 2004 Hyundai Elantra that is giving me problems. The first time I start it each day it will start but then the engine sputters then cuts off. I've also noticed that if I can get it to start and put it in reverse or drive the engine will stay running. It only does it when in park, but after I've driven it the problem goes away. Also when I am stopped at a traffic light, my Elantra idles real rough. Please advise as to what I should do. Thank you.

October 27, 2011

Alex	Comments: Is there a way to clean the soot/dirty at the tip of the sensor. My car had a bad airflow meter and was oozing black smoke like diesel engine yet its petrol. Did this not affect the O2 sensor and do I need a new one or the is way of cleaning as we do for spark plugs????
October 21, 2011

Adeel	Comments: Hi, I want to ask problem in oxygen sensor always lightens up the check engine light or not???
October 13, 2011

Dumbfounded	Comments: I have a 2005 Jimmy. Fuel mileage has gotten really bad, about the same time I started getting a bad vibration in the truck but only when I press down the accelerator. It also idles kind of rough like its missing but theres no service or engine light on. Is this likely to be the 02 sensor?
September 16, 2011

juko

Comments: check engine light on,engine almost or even switches of especially when on drive gear and you step on break.computer diagnostic shows trouble code p0172 fuel sys-rich bk1.what does it mean and whats the solution?thankscheck engine light on,engine almost or even switches of especially when on drive gear and you step on break.computer diagnostic shows trouble code p0172 fuel sys-rich bk1.what does it mean and whats the solution?thanks

August 25, 2011

sam	Comments: have a 1997 yukon 5.7 liter its been missing and fouling the plugs. I changed plugs, wires, cap rotor and coil problem persists. looked for vacuum leak couldnt find one but I may have missed it. oxygen sensor maybe?
August 14, 2011

Andi

Comments: I have a 2004 basic cavalier. About 2 months ago I had a new engine put in. When I got it back it was making a rattling noise at crank up and when I cut it of, like something was loose. It also makes this rattle noise when I stop on an incline and put it back into drive. It never makes it while I'm driving the car, but also when I'm parked in the driveway for a few minutes letting it idle. I can put it in drive and move it just a little, put it back in park and it stops, then rattles when I cut it off. I was told it was the motor mount, supposedly had it fixed, but it still makes this rattle noise. Any ideas.

August 10, 2011

grandammy

Comments: 2001 pont g-am, my codes p0141 & p0171 started 2008 service engine soon came on, check engine light didnt come on till 2010 pulled codes originally just p0141 only one. 08/05/11 is when p0171 started. car is no longer starting. acts like it doesnt have fuel but does have 1/2 tank of gas. it will turn over and stay started about 20 sec then cough*ckoke*gasp nothing. I do have a leak by timing belt gasket but feel this is not a reason for not starting. I really need help on this none of the article i have been reading say anything about the problem I am having. I appreciate all info and answers you may have for me. thanks

August 8, 2011

Nick	Comments: My 2000 honda civic si has the check engine light on, and i think its my o2 sensors, but im not sure if that would cause the light to come on, also it is very underpowered. It also idles really low and idle bounces up n down as well. Please Reply
July 15, 2011

wolfeman

Comments: I have a 99 Firebird 3800 V6.97000 miles,just replaced engine with a 76000 engine .Mechanic says I have a dirty injector.Checked on computor and it says cyl 4 runnig rough. have replaced the injector,the coil,the plug wire and the plug.Still runs ruff at times,at time runs great ,no prob at hiway speeds.Service light came on and stays on.Any suggestions?#4 plug is really bad to replace.

July 1, 2011

Ali G	Comments: I have a 2.0l 2001 Kia Sportage, it runs rough at idle and loses power when driving. The engine check light is on permanantly. Any ideas?
June 8, 2011

doc	Comments: i have a 2000 pontiac bonny ssei super charged. 1 upstream and 1 downstream 02 heated sensor. upon fast acceleration the super charger kicks in. do both sensors have to be in good operating condition or will it run fine with 1 bad and one good sensor. right as i kick in supercharger it will cut out bad and jerk or lose power. cat conv. 02s
June 3, 2011

dasnay	Comments: I own a 1999 Volkswagon Jetta with a bad O2 sensor. Should I be worried about looking into any other underlying problems? The warranty will be up soon... thank you for your time
May 11, 2011

daddyd

Comments: 0n the 4 wire upstream 02 sensor can u test it on the bench and what wires do u test color code white,blue 2 black. what 2 set ome miter at what wires to test? on car same-thing what wires what to set volt meter at also what are the setting suppose to be on both omes,volts. i appreciate any help u can supply as i have put 2 new sensors from napa,autozone kept getting code p0032 van runs great no odor or anything? it is a dodge caravan 04 3.3 eng.

thank u aldi

May 10, 2011

car salesman	Comments: 2004 Dodge Intrepid 3.5 engines are notorious for sludge and having numerous mechanical problem. They usually don't live past 8 years...
April 28, 2011

Frank	Comments: Hey,I just sent a question but let me add some more information about the 2004 Intrepid 3.5. When it does this it gets fault code P0171 and P0174, Lean / rich mixture on bank 1 and bank 2. I figured it was acting lean, but the info above say's bad oxygen sensor would make it run rich. That's why I pulled the plugs to see if they were wet. And they were dry.
April 24, 2011

Frank	Comments: I have a 2004 Dodge intreped 3.5. Then it gets warmed up it starts missing, gradually gets worse and wont' run, wont' start till it gets cooled down, It will restart in an hour, maybe sooner. Runs fine when cold. Plugs look good, and dry when I pull them out right after it won't start. I am guessing its the oxygen sensor. Is that likely.
April 24, 2011

Russ	Comments: Hi thanks for your advice.....i took the car back and a fault code read "Converter lock out - excessive slipping....the garage replaced the new second hand ! converter with a recon one....problem is exactly the same....all been checked for air leaks and there are none...the garage seem to be at a loss...any help......please
April 20, 2011

Russ	Comments: I ve just had the torque converter replaced on my BMW 330CI. Since getting the car back ive noticed that the car seems to be running sluggish. On the motorway if iam driving along around 60 - 70 MPH and i put my foot easy on the accelerator there seems to be no response. The petrol gauge goes up but the rev counter stands still. Eventually the car gains pace and still drives superb at higher speeds or when i kickdown. There have been two codes recently pointing to the o2 sensor post cat bank 2 but i had one of these changed a couple of months ago. At the moment there are no warning lights on...iam hoping theres some sort of air leak and its not a transmission problem starts fine and idles fine changed the plugs but no change...any thoughts....
March 28, 2011
	Followup from the Pelican Staff: Hmm, if you've had the torque converter replaced recently, then I would take a closer look at that being the problem. On the freeway when you step on the gas, the engine will try to push the car faster through the transmission, which includes the torque converter. If there's something wrong with the converter, then I think you might see some of the issues that you're thinking you see. I would take it back to them and have them read the codes and drive the car for a while to see if there are any issues. - Wayne at Pelican Parts

mmm3	Comments: Wayne, I have recently purchased 2001 e46 m3 and I do not think it is producing enough power compaired to another one I drove a year ago. The Vanos unit was replaced at the dealer some time ago, do you think I should check the cam timing?? incase they stuffed up? or any other ideas??? apart from that all service items seem to be up to date.
March 24, 2011
	Followup from the Pelican Staff: It's impossible to tell and compare to a car you drove a year ago. If you think that something is amiss with the car, then pull the codes and see if there are any problems. If you think the cam timing is off, then you can plug it into the computer and read it and check it against the spec. - Wayne at Pelican Parts

nissan king	Comments: is it possible for the converter to be clogging or clogged already and causing more codes to show on a scanner? if so what are other things that may happen? Thanks!!!!n
March 16, 2011
	Followup from the Pelican Staff: Yes, it is possible for the catalytic converter to be clogged - that would typically show up as a post-cat O2 sensor error. The secondary oxygen sensors are installed in order to monitor the performance of the catalytic converters. If they don't read what they are expecting to read (based upon the values from the pre-cat sensors), then they will trigger fuel injection error codes. - Wayne at Pelican Parts

Munya	Comments: I have had my car for 18 months its got 300k kms on the clock been driving well untill some 400kms ago. The fuel gauge became faulty giving false readings, car suddenly lost power on an uphill on one of my drives and I assumed i was running low on fuel. Waited a while and restarted the car it was misfiring, drove the car to the nearest fuel station refueled and the car was okay. The problem became more frequent at times the car would just cut off when idling and required a great deal of patience to start it. When cold it starts well but after 5kms or so it would start misfiring again took it in for diagnostics and did not find any joy. It seemed like there was a leak somewhere on the intake manifold because after spraying a strong brake disk cleaner the revs would go up but even that test was not consistent. The mechanic replaced the centrifugal oil seperator and there was no change. I have since discovered that if I keep running it for say a km or two after it starts misfiring the car will clear the misfire when I start it again but this will last about 8 to 14kms before the misfire comes back again. Out of desperation I took out the catalytic converters because I could pick up a smell like battery acid, assumed it was the cats so took them out. The problem went away for 40km and it started again and the smell is still there. I need your help what do I do????????????
March 16, 2011
	Followup from the Pelican Staff: Sounds like an issue with the fuel injection system possibly. I would check the trouble codes. It's hard to give any more information - you didn't tell me what car you had. - Wayne at Pelican Parts

JNolan	Comments: I have a 1995 BMW 540i that started having a rough idle in cold weather. Then car lost a ton of power. It got to the point that it didnt start at all. Had a new fuel pump and fuse, master cylinder and belts replaced. Car still has check engine light on. OBD code is 1222. We were running it with regular unleaded. Car continued to buck and shudder and would barely go above 10-20 miles/hr. The car almost comes to a crawl on hills. The more gas you give the worse it is. The exhaust smell has a very strong gas smell. Not like rotten eggs but overwhelming smell of gas. Now car will not start at all. Any ideas?
March 5, 2011
	Followup from the Pelican Staff: Code 1222 means that the Oxygen (O2) sensor is detecting a very rich or lean condition. This could be caused by a faulty O2 sensor, or it could be caused by a huge vacuum leak somewhere in the engine. I would perform a check for vacuum leaks in the engine - I have an excellent article on this here: http://www.pelicanparts.com/techarticles/Boxster_Tech/21-FUEL-Vacuum_Leaks/21-FUEL-Vacuum_Leaks.htm I would also think about replacing the O2 sensor as well - that might help clear up the problem. - Wayne at Pelican Parts

Tom	Comments: Thanks for posting the article. I have a 2002 330ci with 99,908 miles when the "service engine soon" light came on and the car has a rough idle but still has decent power. I had AutoZone check for codes and they found four. They are P0171, P0174, P1342, and P1348. When I returned home I discovered I had left the oil fill cap off. My guess is that I drove the car between 170-200 miles like that. Thoughts? Oxygen sensor and or mass air flow sensor? Thanks for the help.
February 15, 2011
	Followup from the Pelican Staff: Other than creating a big mess in the engine compartment, there's no real damage that can be done by driving without the oil cap properly attached. I will admit that I did that once too, and paid for it by having to clean the whole engine. The car is expecting there to be crankcase vacuum, so when there isn't, it will pop codes and run rough. Install the oil cap back on if you haven't already, reset the codes, and then see if they return. - Wayne at Pelican Parts

vinnie	Comments: Wayne - thanks for this, a vacuum leak is what I have been surmising also. Problem is, where are the vacuum lines? other than the large intake boot that I've already replaced? Can you give me a hintfrom this/to this kind of thing? Thanks much.
December 7, 2010
	Followup from the Pelican Staff: Manifold gaskets can also be sources of leaks - you need to trace everything back from the big boot. I wrote an article on checking for vacuum leaks, you might want to check it out here: http://www.pelicanparts.com/techarticles/Boxster_Tech/21-FUEL-Vacuum_Leaks/21-FUEL-Vacuum_Leaks.htm - Wayne at Pelican Parts

Vinnie	Comments: It's a Peake code reader. The codes are: E4 - 02 sensor adaptation limit cyl 4-6 E3 - 02 sensor adaptation limit cyl 1-3
December 6, 2010
	Followup from the Pelican Staff: Okay, this error can mean that the O2 sensors are reading levels that they should not have been reading (beyond their range). With multiple bank errors like this, it typically means something else is wrong and the fuel injection system cannot adjust properly. The first thing I would look for would be a major vacuum leak - check to see if that is affecting the mixture and metering of the fuel injection. - Wayne at Pelican Parts

Vinnie	Comments: 2001 330i - I keep getting an E3 and E4 fault code about once a week. I replaced the pre-cat oxygen sensors two months ago, along with a new intake boot both parts, cleaned the air mass sensor, new NGK plugs, new fuel filter, new exhaust camshaft position sensor. Could this be the post-cat oxygen sensors? Also, is there any other vacuum lines to check besides the main large intake boot and flexible tube attached to it?
December 3, 2010
	Followup from the Pelican Staff: E3 and E4, I'm not familiar with what those codes mean, which reader are you using to get them? - Wayne at Pelican Parts

safetylea	Comments: above item sounds like my 93' custom made concept Thunder Storm SS with the Isuzu 1.6 geo Storm Motor Will get and install new Oxygen sensor today......
November 12, 2010

chefrob15	Comments: i own a 1979 mercedes-benz 280 e and i think my oxygen sensor is bad because i am getting poor mpg. i recently had a tune up and the oxygen sensor was not replaced . i have had the car for going on 3 years and have had it tune up twice .could the oxygen sensor be whats causing it to get poor mpg?
October 27, 2010
	Followup from the Pelican Staff: It might be. The fuel injection systems in those days were very primitive in those days, it may or may not be the problem. They are about $30 to replace, I'd say it can't hurt to start there.- Wayne at Pelican Parts

Nisha	Comments: I have a 1997 BMW 528i. My car has lost a lot of power. I can push the petal to the floor and the RMP's when rise faster then the MPH. The car jerks then speeds up as it changes gears. The cats are not the problem. I already had the taken care of and the problem still exist. I haven't changed the fuel filter yet b/c i don't know if that could cause my car to loss so much power. My car also starts to run hot when i turn on the defrost or the seat warmers. then when i speed up it cools down. I'm thinking i need a raditator fan and a Mass Air Sensor. But I know nothing about cars. Any help? This is drving me crazy.
October 15, 2010
	Followup from the Pelican Staff: You need to read the codes to see what the issues are, see here: http://www.pelicanparts.com/bmw/techarticles/Mult-Code_Reading/Mult-Code_Reading.htm The car should give you an indication of what is wrong with it through the DME codes. - Wayne at Pelican Parts

GeneO	Comments: I have a 2004 X3 3.0l engine that that runs rough then turns off above 9700 feet. Head back down the mountain and the engine runs great, good fuel economy-power-etc. OB II analysis is a green light and reveals no error code. This is very inconvenient living in Colorado, any ideas. Thanks
October 6, 2010
	Followup from the Pelican Staff: The mixture gets a bit rich at higher altitudes due to the less-dense air. All modern fuel injection systems have some method to determine the density of the air. I'm not specifically sure about the 2004 model - it may be built-in to the mass air flow sensor (MAF). I would check, and if there is no specific altitude (air pressure sensor or barometer), then I would think about replacing the MAF as a potential solution to the problem. - Wayne at Pelican Parts

beast	Comments: My daughters 2001,330i started suddenly running rough. Its real bad at idle. I pulled the codes. Three were for misfiring cylinders and one for a,"slow response oxygen sensor bank 2 sensor 2." I just had the A/C serviced and she said she almost ran out of gas right before it started running rough. Could the fuel filter be plugged?
July 8, 2010
	Followup from the Pelican Staff: If the O2 sensor is giving a fault code like that, I would reset the codes and see if it returns. - Wayne at Pelican Parts

galo	Comments: hello..i didnt receive but a link to this page...where's the answer to my cuestion
June 23, 2010

cooper s	Comments: i have a 08 mini cooper s and it misfires only for 10-15 seconds after a cold start and seems to be overheating slightly. could this be a o2 sensor?
June 22, 2010
	Followup from the Pelican Staff: It could be. I would get a Peake Research reader and pull the codes. I don't have a MINI specific article up just yet, but this one is very similar: http://www.pelicanparts.com/bmw/techarticles/Mult-Code_Reading/Mult-Code_Reading.htm - Wayne at Pelican Parts

actuator	Comments: actuator's solution. Found that my o2 sensor heat relay was not quite seated all the way. Noticed the relay next to it was the same part number too. Swapped relays and check engine light went away immediately after starting car. Thank you for your article on o2 sensor troubleshooting. It was very informative.
June 5, 2010

actuator	Comments: I have a 1996 bmw 318ti. My service engine light came on and I went to Autozone to have them read my codes. They showed me that my car had a "faulty HO2S11 bank 1 sensor 1" In other words a faulty upstream of the catalytic converter 02 sensor. they said my car would use the Bosch p/n 13559 sensor. installed sensor and light was still on. They reset the light and it came on again 20 miles later. Is the 13559 the correct part? I cleaned the old one and it worked for a while about 10 miles. Any suggestions? Thank you in advance. actuator
June 3, 2010
	Followup from the Pelican Staff: Two suggestions - it may be the wire harness is having trouble, or you may have replaced the wrong bank? - Wayne at Pelican Parts

JD	Comments: I have a 2005 Nissan Altima 2.5L. Just recently the engine light came on. When I try to start the car it doesn't start right away. It seems like it's not getting gas. The car will start after a few minutes of trying. Would this be caused by the O2 sensors or the catalytic converter going bad?
May 25, 2010
	Followup from the Pelican Staff: It could be caused by just about anything. Pull the trouble codes and they will tell you most likely where the problem lies. - Wayne at Pelican Parts

Lou	Comments: I've recently had mechanic drop the pan, drain the transmission fluid in which 75% was changed, they checked magnets and found some slushy build up but not excessive, and they changed the screen. This is as much of a tranny service they recommend.
May 25, 2010

Lou	Comments: Wayne, Thanks for the response. I've had three transmissions mechanics test drive it and none of them think it is a transmission problem, of course none actually felt the symptoms of power loss and high rpms during the test drives. I've taken the Infiniti to the BEST transmissions shop in my city of 1.7 million residents, and he is now refering me to an electrical specialist to test the speed sensors and more. Oh, I forgot to mention that codes being given are for SPEED SENSOR not sure which one and CATALYST SYSTEM EFFICIENCY BELOW THRESHOLD. From what I have read, many others with the same symptoms as my car have solved the problem by replacing the necessary speed sensors. I'm really of skeptical of any mechanic who insists on overhauling the transmission without even doing a minimum diagnostic, which in my book should involve testing the speed sensors. Any thought on this? Thanks
May 25, 2010
	Followup from the Pelican Staff: "Of course none actually felt the symptoms of power loss and high rpms during the test drives" Right, so they haven't seen the problem. I would change the fluid in the transmission and cross my fingers. - Wayne at Pelican Parts

Lou	Comments: I have an Infiniti i30 2001 with 120,000 miles. Problem is: Almost daily the car will lose power while going some 20 - 40 mph and rpms will shoot up to almost 4000. It feels as if transmission were slipping. Each time this happens I have to pull over, shut off the engine and turn it back on to continue with my trip. I've taken it to several mechanics. All have ruled out any transmission problems. When they do a computer scan, codes for catalytic convertor pop up. One mechanic says that Nissan says to not touch catalytic, instead to change the o2 sensors. Well, i've changed both rear o2s and now this mechanic says both front ones should be changed. Any advice? I realize I am over the factory 100,000 suggested miles, at 120k, but could the o2s really be causing this? Oh yeah, also engine is running rich.
May 22, 2010
	Followup from the Pelican Staff: This sounds like an intermittent transmission problem with nothing to do with the O2 sensors. I would focus further attention on the transmission. - Wayne at Pelican Parts

TEEM	Comments: I have a 2007 Audi A4 3.2L. It sometimes hard starts turns over for 10-15 seconds before it fires, but runs and idles fine, though the exhaust smells rich, runs hot and blows out some black smoke when it's cold. When I am accelerating at between 1500 and 2500 RPM in the higher gears, I get a random misfire. I have recently replaced the plugs and coil packs, as Audi has a Maintenance Campaign out for the packs, and it was diagnosed today as having a bad o2 sensor. Could it be just a sensor? Or could it be something more? Thanks.
April 29, 2010
	Followup from the Pelican Staff: The O2 sensor could cause performance issues, but I don't think it would cause the types you're referring to here. I would get an OBD-II code reader and see what other codes are being tripped by the computer. - Wayne at Pelican Parts

Walt	Comments: I have four o2 sensors. two in front of cat. converter and two behind. Dual exhaust. After engine warms up it runs rich and idles rough. When I accelerate it blows out a cloud of black smoke.I've replaced all the o2 sensors,but not all at the same time. any suggestions?
April 18, 2010

Jeff	Comments: Canuck Van, all dodgesmaybe other brands too? have a built in diagnostic code reading facility.. Early models like my '94 b250 van show the codes as a series of blinks through the engine light, and newer ones with digital dashboards show them as actual codes in the odometer.. google dodge trouble codes or something till you find the procedure.. it works, I've confirmed it.
April 5, 2010

kels

Comments: My service engine soon light came on. I took it to a shop and the guy there said it was the oxygen sensor and that sometimes they just get dirty or moisture builds up on them and they misfire or misread. He turned off the light but didn't replace the sensor. He said to drive it a while and if the light comes back on then to bring it back. Will this do anything to my car? I have a trip coming up where I'm going to be driving almost 200 miles, will this be bad for my car?

April 1, 2010

BO	Comments: 1988 325ic check engine light is on , fault code found OA oxygen sensor faulty? thanks
March 27, 2010

Richie	Comments: i have a 2002 ford explorer and it cuts out real bad and dies alot but only when im stoping does great on highways and mpg hasnt droped dramatically! possible o2 sensor is bad?
March 17, 2010

Wayne at Pelican Parts	Comments: test comment
March 11, 2010

pattyotool	Comments: My check engine light is on, I believe my oxygen sensors may be bad. However the engine also surges at half speed and gets worse when I open the throttle. I replaced the plugs and the fuel filter which was bad. Not sure if I change the sensors that will repair the problem.
February 22, 2010

stringer	Comments: My car has 2 O2 sensors before the cat and 2 O2 sensors after the cat. It's a '99 BMW M3 One of my pre-cat sensors indicated bad from the scan tool. Do I have to replace both pre-cat sensors, or just the bad one? The car runs fine, and only has 45,000 miles.
February 22, 2010

Raymond	Comments: Vey good article, alot of great info for trouble shooting.
February 12, 2010

sonny	Comments: this could apply to my Hyundai Santafe 2002. Really bad smell of unburned fuel during start up and when I park and open my door. Fuel consumption at aroung 3.5 to 4 Km/liter. do i need to replace my sensor? recently had the spark plugs replaced and the vaccuum hoses checked all ok still the same lackluster performance. thanks for any advice.
February 2, 2010

Alan

Comments: I have a 2000 Hyundai elantra and it starts fine, but sometimes it misfires really bad and i have to turn it off. I'm thinking its the O2 sensor because its running very rich, to the point that i have to close my front door because the smell of unburned fuel is really bad and there is a black liquid coming from the exhaust. Also, the "Check Engine" light comes on when its idling and sometimes it starts flashing. Most importantly it chugged 3/4 of a tank of gas for five miles that I drove it! I appreciate any thoughts, thanks!

December 22, 2009

Canuck van	Comments: Thanks for the article. After new plugs, wires, and air filter, my 1990 Caravan 3.3L starts fine, idles fine, and revs fine in neutral BUT as soon as I put it in gear and accelerate even slowly, it starts misfiring after about 1600 rpm, and it craps out unless I ease off the pedal...I've pulled the 02 sensor 4 wire and the shield vents aren't blackened or plugged...I don't have a digital voltmeter. Do you think its the 02 sensor?
December 10, 2009
	Followup from the Pelican Staff: Your car will output trouble codes - you need to figure out what codes are being triggered, otherwise it's just guesswork. The Durametric tool we sell should help diagnose this, or you can take it to a good independent shop that has an applicable tool. - Wayne at Pelican Parts

oldie	Comments: check points? Doubt any cars with an o2 sensor had points.
November 2, 2009

onin	Comments: hi there.. i have a 2003 honda city i-dsi with the same symptoms stated above. i already had a check run to the computer system and it was pointing to the o2 sensor of code 2 i think.is it the o2 sensor already? thanks a lot
October 20, 2009
	Followup from the Pelican Staff: Yup, sounds like it's the 02 sensor. - Wayne at Pelican Parts

CcRider	Comments: Some sounds like it applies to my problem 97 geo prism, code shows bad O2 sensor however the car only misses bad when its cold soon as I drive a couple miles its smooth as silk & no miss fule ecomemy seems pretty good on it.
October 15, 2009

Curtis	Comments: Excellent article. I appreciate the tips and symptoms, especially.
May 21, 2009

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Pelican Technical Article:

About Oxygen Sensors
Jared Fenton

When should I replace the oxygen sensor?

What are the symptoms of a bad oxygen sensor?

What can damage the oxygen sensor?

Is it safe to test an oxygen sensor?

How does this thing work?

Oxygen sensors usually put out a very small voltage when measuring oxygen content. Typically, they only put out from 0 to 1.1 volts max.

All internal combustion engines need a proper air-fuel ratio in order to run correctly. Gasoline engines need to run a ratio of 14.7 parts of air to one part of fuel. (Air cooled motors typically need to be slightly richer).

How do I test the sensor?

The first step is to get the engine warmed up to operating temperature. This insures that the oxygen sensor will generate voltage. Now, attach the positive lead of the voltmeter to the oxygen sensor output wire.

Pelican Technical Article:

About Oxygen SensorsJared Fenton

When should I replace the oxygen sensor?

What are the symptoms of a bad oxygen sensor?

What can damage the oxygen sensor?

Is it safe to test an oxygen sensor?

How does this thing work?

Oxygen sensors usually put out a very small voltage when measuring oxygen content. Typically, they only put out from 0 to 1.1 volts max.

All internal combustion engines need a proper air-fuel ratio in order to run correctly. Gasoline engines need to run a ratio of 14.7 parts of air to one part of fuel. (Air cooled motors typically need to be slightly richer).

How do I test the sensor?

The first step is to get the engine warmed up to operating temperature. This insures that the oxygen sensor will generate voltage. Now, attach the positive lead of the voltmeter to the oxygen sensor output wire.

About Oxygen Sensors
Jared Fenton