Parts Catalog Accessories Catalog Tech Info Tech Forums
 
Follow Pelican Parts on Facebook Follow Pelican Parts on Twitter Follow Pelican Parts on Instagram Follow Pelican Parts on YouTube Follow Pelican Parts on Pinterest Follow Pelican Parts on Tumblr
  Search our site:    
View Recent Cars  |   Cart  | Project List | Order Status | Help    
 >  >
Oxygen Sensor Replacement
 
Bookmark and Share

Pelican Technical Article:

Oxygen Sensor Replacement

Nick Czerula

Time:

3 hours3 hrs

Tab:

$300

Talent:

****

Tools:

Oxygen sensor socket, 22mm wrench, flathead screwdriver

Applicable Models:

BMW Z3 (1996-02)

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 are used to monitor the oxygen content of engine exhaust. That information is used by the engine control module to fine tune the amount of fuel supplied to the fuel injectors. In the BMW E46 6-cylinder engine, a pair of oxygen sensors are installed in the exhaust manifolds just ahead of the catalytic converters and another pair is in the pipes just after the converters. 

Once the engine reaches operating temperature, output from the precatalyst pair of sensors settles into a steady wave pattern between 0 and 1 volt. The lower limit indicates a lean fuel mixture (extra oxygen in the exhaust) that the ECM corrects for by increasing the fuel supply. This leads to a richer mixture (low oxygen content in the exhaust) and a higher voltage produced by the oxygen sensor; the ECM then reduces the fuel amount and the cycle continues in this fashion, producing what is called a "closed loop" operation.

The post-catalyst pair of oxygen sensors ideally detects a steady and unvarying amount of oxygen exiting the catalytic converters. The ECM uses this information to monitor catalytic converter efficiency.

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 them, as damage may occur. Also, keep the sensor tip clean when reinstalling the sensor.

Oxygen sensors are laid out in banks that refer to cylinder numbers and the sensor numbers referring to before or after the catalytic converter. On 4-cylinder models Sensor 1 is the pre-catalyst sensor and sensor 2 is the post-catalyst sensor.

On 6-cylinder models, 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.

In this tech article I will show to you how to replace the oxygen sensors on a 4-cylinder Z3. 6-cylinder models are similar. I will highlight the locations of the sensors on 6-cylinder models to help when you have to deal with them.

To avoid marring the paint and trim, work with a plastic prying tool or wrap a screwdriver tip with masking tape before prying out body or interior items.

Keep in mind that when your car was serviced before, parts may have been 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 are 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. Do not work on your vehicle if you feel the task is beyond your ability. 

Vehicle models change and evolve, as they grow older, so the vehicle shown in our illustrations may vary slightly from yours. 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.

On 4-cylinder models: Bank 1 Sensor 1, green arrow.
Figure 1

On 4-cylinder models: Bank 1 Sensor 1, green arrow. Bank 1 Sensor 2, yellow arrow.

On 6-cylinder models: Bank 1 Sensor 1, green arrow.
Figure 2

On 6-cylinder models: Bank 1 Sensor 1, green arrow. Bank 2 Sensor 1, yellow arrow, Bank 2 sensor is hard to see in this photo, yellow arrow points to where it is. It is buried beneath the ignition wiring harness. The electrical connectors are mounted below the valve cover (red arrows).

Bank 1 Sensor 2, green arrow.
Figure 3

Bank 1 Sensor 2, green arrow. Bank 2 Sensor 2, yellow arrow. The electrical connectors cannot be seen in this photo. Follow the harness up to locate them. Replacing sensor before catalytic converter

Locate oxygen sensor electrical connectors at transmission bell housing, mounted to the transmission pan.
Figure 4

Locate oxygen sensor electrical connectors at transmission bell housing, mounted to the transmission pan. (green arrows). Label or mark connectors to aide during reinstallation. On 6-cylinder models, I suggest replacing one sensor at a time so you do not mix up connectors.

Next, disconnect electrical connector of oxygen sensor you are replacing.
Figure 5

Next, disconnect electrical connector of oxygen sensor you are replacing. (green arrows) First, remove the electrical connector from the mounting bracket by pulling it straight out. Once out, disconnect electrical connector by pulling it apart.

Using an oxygen sensor socket, remove oxygen sensor from exhaust.
Figure 6

Using an oxygen sensor socket, remove oxygen sensor from exhaust. If you donÂÂ't have an oxygen sensor socket, use a 22m box end wrench. Lightly coat new oxygen sensor thread with anti-seize compound. Install new oxygen sensor and tighten to 50Nm (37 ft-lb). Then reroute wiring harness and connect electrical connector. Repeat if replacing both sensors. Then reassemble engine covers and clear any engine fault codes using a BMW scan tool. Replacing sensors after catalytic converter Oxygen sensors are located in exhaust, behind catalytic converters.

Locate oxygen sensor electrical connector, it is mounted to the heat shield near the catalytic converter.
Figure 7

Locate oxygen sensor electrical connector, it is mounted to the heat shield near the catalytic converter. Pull the electrical connector and wiring harness out of the mounting clips (green arrows). On 6-cylinder models, label or mark connectors to aide during reinstallation. I suggest replacing one sensor at a time so you do not mix up connectors.

Next, disconnect the electrical connector of the oxygen sensor you are replacing by pulling it apart.
Figure 8

Next, disconnect the electrical connector of the oxygen sensor you are replacing by pulling it apart.

Using an oxygen sensor socket, remove oxygen sensor from exhaust pipe.
Figure 9

Using an oxygen sensor socket, remove oxygen sensor from exhaust pipe. If you donÂÂ't have an oxygen sensor socket, use a 22mm box end wrench. Lightly coat new oxygen sensor thread with anti-seize compound. Install new oxygen sensor and tighten to 50Nm (37 ft-lb). Then reroute wiring harness and connect electrical connector. Then and clear any engine fault codes using a BMW scan tool.

Bookmark and Share
Comments and Suggestions:
Bruce Comments: do faulty oxygen sensors cause heavy miss fire's on a z3 2lt 2000 automatic? Why are there so many oxygen sensors on this car?Thanks!
August 25, 2016
  Followup from the Pelican Staff: Oxygen sensors do not cause a misfire. There are four sensors to monitor themixture and catalytic converters. - Nick at Pelican Parts  
Frank C Comments: Letting folks know where the connectors are for the 6 cylinder cars would be helpful. Now, I know where they are... Under the central cover over the intake manifold and the rear O2 sensor connectors. Please update the article to include this information.
May 22, 2016
  Followup from the Pelican Staff: We didn't have a 6 cylinder model.

Depending on the year, they are either attached to the fuel rail like yours, or in the valve cover valley near the coils. - Nick at Pelican Parts
 

  Search our site:    

View Cart & CheckOut | Project List | Order Status |  Help    

 

[Home] [Customer Service] [Shopping Cart] [Privacy Statement]
 [Contact Us] [About Us] [Shipping] [Map to our Location] [Careers]

Copyright © Pelican Parts Inc.

Page last updated: Sat 12/3/2016 02:06:51 AM