O2 Censor

[San&Mar]

Just bought a 93 325is from a friend. Took it to get smogged and it didn't pass. Just got a new 02 censor and new catalitic converters put in as well and the "Check Engine" light keeps coming on and the code on smog keeps saying it's the O2 censor. My mechanic works on nothing but BMW, Mercedes and Porche's. He's about to lose the last of his hair trying to figure out what's going wrong. Anybody been there or done that? used

[BMWJNKY]

What is the exact code for the O2 sensor? With out the exact description of the code it is hard to tell what could be the cause. There are numerous codes that are O2 sensor related but don't meen the O2 sensor is bad.

[San&Mar]

Where on the Smog Check Vehicle Inspection Report do I get the O2 censor
code from? %O2 column?

[BMWJNKY]

You will have to ask the mechanic that pulled the code for the exact description if it isn't on the workorder. The paper that has O2% and other percentages on it is only what exhaust gas percentages were measured comming out of your car.

[MrM3]

->moving to E36

[NID2]

What test to perform to make sure:
• The first is a carbon dioxide test performed on the cooling system will tell you if C02 is going inside your coolant.
• A leakdown test will allow you to check each cylinder to look for pressure loss inside the cylinder. Failing the test could also be seepage past a bad valve guide, piston ring...
Head Gasket Testing Kit


The best method is to have a service shop, or a friend who owns a block test kit test your system for a compression leak to your cooling system. I heard that some test kits can be purchased from auto stores. This is a test unit and test fluid that changes color with the presence of exhaust gas in the engine coolant. Another test that should be completed is a coolant system pressure test Test your system for leaks with nine to twelve Psi pressure. It should not show any appreciable pressure loss within 5 minutes.

Sometimes it's worth it just to have a pro shop diagnose the problem, even if you are planning to do the repair yourself.