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I have a question about wiring of an O2 sensor in my 1987 190E 2.3 16V. I purchased a replacement O2 sensor but the power connection plug is different than what is on my car and the two wires on the 2 sensors are white. How do I determine which white wire is the ground or the positive, or does it matter?
190E 2.6L 1989, 190E 2.6L 1988, BMW 535dXdrive 2014, BMW 428i 2015
Most likely the white wires are for the heating element. There is no wire for sensor ground. it is single ended and uses the chassis as ground.
To make sure measure the resistance to chassis from either white wire to chasis ground after you unplug it. My guess is you will see an open or a non zero resistance,
In that case it does not matter.
Also measure the resistance of either lead on the sensor side to ground. If that is also open it probably does not matter and just trust the polarized connector.
the white wires are definitely for the heating element. The issue is that I had to cut the connector that was not compatible with my car and solder to the old connector. On the sensor side, if I measure continuity between the white wires and the chassis ground, Should one be open and the other closed? I appreciate your help on this. My car is not running well and I want to make sure I do this right first.
190E 2.6L 1989, 190E 2.6L 1988, BMW 535dXdrive 2014, BMW 428i 2015
One of the wires on your car side is brown, so I suspect that is a ground, please check that. If so check that none of your white wires are not grounded to the chassis/body of the O2 sensor.
Neither white wires on the sensor side are grounded to the chassis. I am still not which one of the two white wires should be connected to the ground. I am found to assume it does not matter which one for now.
190E 2.6L 1989, 190E 2.6L 1988, BMW 535dXdrive 2014, BMW 428i 2015
I suspect it is common to not have heating elements connect to ground for safety reasons. If neither the sensor side or the ECU side had a path to ground you should not try to connect any wire to ground either. Unfortunately my wiring diagrams do not include the O2 sensor so I can inform you with confidence.
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