BMW and MINI DIY Video – Replacing Oxygen Sensors, O2, OBD-II, How To
The Bavarian Autosport Ultimate Maintenance Schedule (blog.bavauto.com/go/maintenance) is invaluable for BMW and MINI owners who wish to do all they can to keep their Ultimate Driving machines in top shape. At BavAuto, we have been working on completing sample DIY videos for each of the maintenance tasks listed on the Ultimate Maintenance Schedule. In this DIY video we will show a common oxygen sensor replacement.
BMWs and MINIs have two basic styles of oxygen sensor locations. The early BMW models, through 1995 have one sensor (two for V8s) mounted just ahead of the catalytic converter (one for each side, on V8 models). These sensors are generally accessed from under the car. Some models allow access from under the hood, as shown on a 1989 325is in the photo DIY article in the Fall 2004 issue of Fast Times (click HERE to see the article). Models produced for model year 1996 and later, must comply with the OBD-II (On Board Diagnostics v-2) mandates and have sensors mounted ahead of the catalytic converter(s) as well as behind the converter(s). Additionally, there will be a pair of before and after converter sensors for each “bank” of cylinders. 6-cylinders, V8s, V10s and V12s have 2 banks and, therefore, 2 before-converter and 2 after-converter sensors. 4-cylinders have 1 bank and just one before and one after-converter sensor.
In this DIY, we will address a typical OBD-II (1996-on) oxygen sensor replacement. We will be showing the very common M54 6-cylinder engine as used in the 3, 5, Z and X models from the 2000s. The before-converter sensors are accessed from under the hood and the after-converter sensors are accessed from under the vehicle. Earlier OBD-II models and V8/V10 models may require access to all sensors from under the vehicle.
Under-hood access to before-converter sensors:
NOTE: Oxygen sensors can be rusted into place. Working on them when they are warm (from the engine running) can help with removal. Be careful of hot engine and exhaust parts if working on a hot engine. Application of a good penetrant, such as the MechanicAll (BavAuto.com) may assist in successful sensor removal.
3) Follow the wiring harness from the sensor to the harness-to-vehicle plug. Disconnect the sensor harness plug from the vehicle harness plug. Release any ties or clips securing the sensor’s harness to the engine or vehicle.
5) Apply torque to the ratchet to loosen and then unscrew and remove the sensor.
6) Install the new sensor being careful to not touch the sensor’s end. Note that there is a pre-applied anti-seize compound of the sensor’s threads.
7) Tighten the sensor to the specified torque (available in the applicable Bentley repair manual). In this case, the torque is 37 ft-lbs.
8) Route the sensor’s harness through any ties or clips and connect to the vehicle harness plug.
9) Repeat 3 through 8 for the other before-converter sensor.