O2 senor madness

[e36_Jeff]

I have a '98 328is, and I failed emmissoins due to a bad O2 sensor. Everything I have read says I have 4 O2 sensors, however, I only have 1 bad one, so I got a new sensor. I got under the car to replace the sensor, and I can only find 2, they are directly behind what I assume are my catalytic converters, and i see no points on the rest of the exahust system that the other O2 sensors should be, Ive checked the book, and it appears that there should be 2 sensors directly before the catalytic converters, but there are no sensors, and no spots where a sensor could be screwed in, and there are no extra plugs under the car for the other 2 sensors, and I dont see any spots where there could have been the mounts for the plugs at any time. basically, Im at a total loss as to what is going on here. any and all help would be greatly appreciated

[paxcam]

The 2 pre-cat sensors are located on the inboard side of your exhaust headers. Check this illustration.

http://bmwfans.info/original/E36/Lim/328i-M52/USA/L/A/1996/01/mg-11/ill-11_1471/

They are visible from under the car.

You should be able to pull a code to tell you which o2 sensor has gone bad-- either bank 1-3 or bank 4-6. Go to Autozone and they'll pull the codes for free.

Good luck.

[e36_Jeff]

according to the DMV readout its bank 1 sensor 1, and thats backed up by a OBDII code reader I have access to, but that makes alot of sense, the repair manual I have says that they are suppoused to be right in front of my catalytic converter, I never looked that far up the line

[Pirate_copy]

Try this mate - http://www.pelicanparts.com/BMW/techarticles/E36-O2_Sensor/E36-O2_Sensor.htm