Expert: Josh Fields - 7/24/2006

Question
Josh,
My 1999 M3 was diagnosed with 2 Oxygen Sensors before the catalytic converter causing a check engine light. I work for BMW of Greenwich so I know I am getting good information. My question is this, will running with this check engine light on until O2 sensors are ordered and arrive do any damage to the car. I am told that the DME will default and simply allow the car to run a bit richer until replaced. Is this about right?

Thanks for the information.
Ron Alberico/BMW of Greenwich

Answer
Ron,
 The information you have is exactly right.  It will just go into "default" mode, and run on factory pre-sets, and disregard any information provided by the O2 sensors.  This doesn't mean that it will damage your car, however it does mean that the DME is ignoring the O2 sensors, and doesn't adjust fuel levels for better emissions.  I think you'll be fine until you get the new O2 sensors.  I have heard of people ruining their Catalytic Convertors by doing this for extended periods, but I dont think you will have this problem.

 Good luck,
 Josh