My check engine light came on on my 97 328i and I took it to the dealer. They said the OBD said it was a bad catalytic converter. Since they wanted $2200 for the part, I bought an aftermarket and had my mechanic replace the whole exhaust from the manfold to the exhaust tips. While he had it up I decided it would be wise to replace the Oxygen sensors at the same time. I bought two Borsch -one before and one after the catalytic converter. The light was off about a week and came back on. The OBD this time said :"BBH02S12 sensor heater circuit" Explanation Open or short circuit condition- probable cause - poor electrical connection, faulty H02s. My question is aren't there only two Oxygen sensors on the car? Since they are both new, I am guessing that there could be a bad electrical connection, or unlikely a faulty new part. Does anyone have any other ideas??
Not sure about the codes you are getting. But your car has FOUR (4) oxygen senors. Two before the cats and two after. See the diagram here. http://www.realoem.com/bmw/showparts.do?model=CD33&mospid=47501&btnr=18_0253&hg=18&fg=10 Note item # 15 & 16 and that it is calling for 2 oxygen senors in each location. I have a 98 328is and I have four O2 sensors. These codes might be unrelated to what you were getting earlier or they could be connected. Take your car to an experienced independent BMW Mechanic who has the computer software to diagnose your car correctly. You can find one in your area by going to http://www.bimrs.org/ Good Luck
Oxygen Sensors Not only do you have 4, but they are heated. Therefore problems can occur in two places, in the sensor, and in the heater circuit. Mechs who know what they are doing can check for both. But the problem could also be elsewhere entirely. For example, I read recently that a clogged crankcase ventilation circuit can give a bad HO2 sensor reading. This is a real problem with computer based diagnostics -- just like in regular computers, the error may not be at all what it says it is. I have the exact same problem as you on my 96 328i -- check engine light comes on, scan says bad number 2 front sensor. Replace sensor, check engine light comes back on again. Possibilities: bad wiring, bad cat, bad computer. Needs somebody with proper tools who can also THINK to solve this. BIMRS.ORG recommendation above is great. I will post how mine eventually worked out. What did you end up doing? Or are you still driving around with the check engine light on?
Oxygen Sensors Dealer list on each sensor is... $250 apiece! Even at the $160 I paid to replace one (that was perfectly good), I resent throwing money away unnecessarily on parts when it's the mechanic's job to find out what's really wrong first.
Contact me if you'd like factory O2 sensors. I own a parts store and sell parts substantially below dealer price.
