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Oxygen Sensor N54 Engine Replacement
 
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Pelican Technical Article:

Oxygen Sensor N54 Engine Replacement

Nick Czerula

Time:

3 hours3 hrs

Tab:

$200

Talent:

*****

Tools:

Oxygen sensor socket, universal-joint adapter, flathead screwdriver, 10mm socket, floor jack, jack stands, wheel chocks, safety glasses, torque wrench

Applicable Models:

BMW 535i/xi Sedan (2008-10)
BMW 535xi Wagon (2008)

Parts Required:

Oxygen sensors, anti-seize paste

Hot Tip:

Work with a cool exhaust

Performance Gain:

Remedy fault codes and maintain proper running engine

Complementary Modification:

Replace in pairs

Oxygen sensors monitor the exhaust stream, comparing the oxygen content in it to the oxygen content of ambient air. When oxygen content is low, the sensor voltage is high. When oxygen content is high, the sensor voltage is low. The voltage created by the sensor is sent to the DME (engine control module) to help maintain a proper fuel mixture. The mixture preparation is used to keep the catalytic converters running at peak efficiency. The oxygen sensors used in E60 models covered in this article has four wires. Two of which are for oxygen sensor heating and two for the signal. The heater is used to get the sensor online faster. Previously, exhaust heat was used. One wire supplied a ground to the sensor for the signal, and the other is for the sensor signal.

The NG6 (New Generation 6-cylinder engines) utilize a wide band oxygen sensor for the pre-catalyst sensors and a standard Zirconia element for the post-catalyst sensors. Wide band sensors begin to operate faster and provide faster more precise exhaust oxygen content to the DME.

Oxygen sensors should be replaced every 100,000 miles. In a perfect world that would be it; wait until a specified mileage and replace the sensor. However, these sensors fail prematurely, set oxygen sensor fault codes and reduce fuel economy. In this article, I will show you how to identify the location of all four oxygen sensors and how to replace them. You will need an oxygen sensor socket to remove the sensors and remember to always work with a cool exhaust. Oxygen sensors are fragile. Do not drop one as damage may occur. Also, keep the sensor tip clean when reinstalling.

Oxygen sensors are laid out in banks, which refer to cylinders and in sensor numbers referring to before or after the catalytic converter. Bank1 or B1 refers to cylinders 1-3. Bank 2 or B2 refers to cylinders 4-6. Sensor 1 or S1 refers to the sensor before the catalytic converter. Sensor 2 or S2 refers to the sensor after the catalytic converter.

Remember that your car may have been serviced before and had parts replaced with different size fasteners used in the replacement. The sizes of the nuts and bolts we give may be different from what you have so be prepared with different size sockets and wrenches.

Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If you're working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Never work on your vehicle if you feel the task is beyond your ability.

Our vehicle may vary slightly from yours as models do change and evolve, as they grow older. If something seems different, let us know and share your info to help other users. Do you have questions or want to add to the article? Leave a comment below. When leaving a comment, please leave your vehicle information.

The red arrow identifies Bank 1 Sensor 1.
Figure 1

The red arrow identifies Bank 1 Sensor 1. Bank 2 Sensor 1 is identified by the blue arrow, as viewed from below, through the body with the wheel well liner removed.

Drain the cooling system and remove the coolant reservoir.
Figure 2

Drain the cooling system and remove the coolant reservoir. See our tech article on coolant reservoir replacing.

Working at the vacuum reservoir, mark the vacuum line locations.
Figure 3

Working at the vacuum reservoir, mark the vacuum line locations. Then remove the vacuum lines (yellow arrows) by pulling them straight off the reservoirs. Then detach the vacuum lines from the mounts (green arrow). Remove the vacuum reservoir 8mm fasteners (red arrows). Then lift the reservoir up, detach the vacuum hoses at the bottom and remove the reservoir from the engine.

Remove the engine cover 4mm Allen fasteners (red arrows) and cabin microfilter housing.
Figure 4

Remove the engine cover 4mm Allen fasteners (red arrows) and cabin microfilter housing. See our tech article on engine covers removing.

Then, remove the oxygen sensor electrical connectors from the holders (red arrows).
Figure 5

Then, remove the oxygen sensor electrical connectors from the holders (red arrows). Mark the electrical connectors so they are not mixed up later. Then pull the electrical connectors apart to disconnect them (inset). Once disconnected, remove the wiring harnesses from the mounts (blue arrows). Then feed the harnesses out from behind the cylinder head (green arrow), removing them from any mounts and snagged areas.

The oxygen sensors have an insulating foil shield.
Figure 6

The oxygen sensors have an insulating foil shield. To get the oxygen sensor socket onto the hex of the socket you have to push the foil up a small amount, just enough to squeeze the socket onto the sensor (green arrow). Bank 1 Sensor 1 is indicated with the red arrow. Bank 2 Sensor 1 is pointed out with the yellow arrow. The right inset shows my socket setup. I used an oxygen sensor socket with a 3/8-inch universal joint on a 2-inch extension.

Using an oxygen sensor socket, remove the oxygen sensor from the exhaust pipe.
Figure 7

Using an oxygen sensor socket, remove the oxygen sensor from the exhaust pipe. Lightly coat the new oxygen sensor thread with anti-seize compound. Install the new oxygen sensor and tighten it to 50Nm (37 ft-lb) with a torque wrench. Then reroute the wiring harness and connect the electrical connector. Repeat the same process if you are replacing both sensors. Then reassemble the engine covers and clear any engine fault codes using a BMW scan tool.

The oxygen sensors are located in the catalytic converters.
Figure 8

The oxygen sensors are located in the catalytic converters. Bank 1 Sensor 2 is shown with the green arrow. A red arrow points out bank 2 Sensor 2.






Working at the bottom of the transmission bell housing, remove the oxygen sensor electrical connectors from the holders (red arrows).
Figure 9

Working at the bottom of the transmission bell housing, remove the oxygen sensor electrical connectors from the holders (red arrows). Mark the electrical connectors so they are not mixed up later. Then pull the electrical connectors apart to disconnect them (inset). Once disconnected, remove the wiring harnesses from the mounts (blue arrows). The mounts are spring loaded. Open them while pulling the harnesses out.

The oxygen sensors have an insulating foil shield (yellow and green arrows).
Figure 10

The oxygen sensors have an insulating foil shield (yellow and green arrows). To get the oxygen sensor socket onto the hex of the socket you have to push the foil up (red arrow) a small amount, just enough to squeeze the socket onto the sensor (green arrow). Bank 1 Sensor 1 is shown with a red arrow. A yellow arrow indicates Bank 2 Sensor 1. The right inset shows my socket setup. I use an oxygen sensor socket with a flex-head ratchet. This photo shows the exhaust removed, which is not required for replacement. It just made getting the photos a lot easier. Lightly coat the new oxygen sensor thread with anti-seize compound. Install the new oxygen sensor and tighten it to 50Nm (37 ft-lb) with your trusty torque wrench. Then reroute the wiring harness and connect the electrical connector. Repeat the same process if you're replacing both sensors. Then reassemble the engine covers and clear any engine fault codes using a BMW scan tool.

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Comments and Suggestions:
Jim Comments: The Service Engine Soon light is illuminated on my '08 335i twin turbo. My code reader shows two fault codes: P0155 and P3027. Question 1: It it safe to conclude that I need to replace the oxygen sensor, Bank 2 Sensor 1 or are there other steps I should do first? Question 2: Can I follow the steps in your excellent directions, simply taking note that things are in different locations than in your write up which is for a different model? see attached picture #3: The Bentley Manual specifies removing the intercooler to get access to the radiator drain plug. Will clamping off the lower hose coming from the fluid reservoir make it unnecessary to drain the system? Thank you very much-Jim
October 25, 2016
  Followup from the Pelican Staff: Clamping it can prevent some leakage, but it may also damage the hose.

Yes, follow the instructions as they apply to your vehicle. Should be similar.

if you have a fault code for the sensor and the exhaust is sealed, it is likely faulty. - Nick at Pelican Parts
 
Vince Comments: I'm trying to change O2 pre cat sensor 1 bank 2 on my BMW 2009 135i, E88 N54 Convert.
July 13, 2016
  Followup from the Pelican Staff: We don't currently have that tech article. If we get a chance to perform the procedure, we will be sure to document it.

I would grab a repair manual. It will have the procedure, special tools and torque specs.

Give our parts specialists a call at 1-888-280-7799. - Nick at Pelican Parts
 
Dash Comments: Hello Mr. Nick thank for e-maling me back on my 10 BMW 535i. I just have one small ? Do ur show a diagram on how to remove the charge pipes? To acscess the front 02 sensor for N54. Do I have to loose the motor mount an jack up the engine?
April 7, 2016
  Followup from the Pelican Staff: See this tech article:

http://www.pelicanparts.com/techarticles/BMW-E60/85-FUEL-N54_Engine_Charge_Air_Duct_Replacing/85-FUEL-N54_Engine_Charge_Air_Duct_Replacing.htm - Nick at Pelican Parts
 
DASH Comments: Hello I have ? Have do u remove O2 on bank ? I have A 10 535i. I see the diagram, but the charge pipe is in the way. Also 02 sensor bank 2 sensor 1 do u remove it remove the bottom?
April 4, 2016
  Followup from the Pelican Staff: if the charge pipe is in the way, you will have to remove it. The pre cat sensors can be removed from the top, post from the bottom. All of the E60 articles are here:

http://www.pelicanparts.com/BMW/techarticles/tech_main_e60.htm - Nick at Pelican Parts
 

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Page last updated: Fri 12/9/2016 02:39:52 AM