Went to Oreilly Autoparts tonight and picked up the Bosch 13942 Oxygen Sensor (for a 1990 Ford Taurus, 5.0 liter Mustang, etc). Here is my question:

-From past posts everyone says you can use this sensor. But it is only a 3-wire sensor. The 1991 535i has a 4 wire. The 4th wire on the BMW sensor is Grey -- I am assuming that is ground? So will this 3-wire Ford sensor work? Do you just not use the gray wire on the original BMW Oxygen Sensor harness?

Thanks
Jeff
1991 535i