BMW: 1995 525i Check Engine light just came on, computer brain, o2 sensor

Question
Good evening Josh,

I found this website given I own a '95 525i since 1999.

Five years ago the garage I am going to in the morning put a used engine in the car; the first owner basically caused the problem.

For the first time I just got the check engine light since 1991 when the used engine was installed.

They work on BMWs and Mercedes in Irvine, California, and have diagnostic equipment.

Any tips for me to make sure I am not overbuying on the diagnosis?

I have added 50,000 miles since 2001 and it was at 45,000 miles in 2001.

Thank you so much,

Deborah Petitti
dlpetitti@cox.net

Answer
Deborah,
 I hope I can help you and possibly save you some money.  Many mechanic's will take advantage of women and their lack of "car knowledge" (not saying that you have none).

 Those cars are equiped with OBD1 (On Board Diagnostics version 1).  The computer (brain/ECU) will take readings from several different sensors, and if any of them are faulty the ECU will light up the "check engine" light.  This is rarely anything of MAJOR concern, probably a dirty O2 sensor or something easily fixed.  Have a trusted mechanic plug a scan-tool into the port in the engine bay, and the car will tell him what is wrong, or at least what made the check engine light come on.  He will look at the cause of the light, and hopefully fix the affected problem.

 Good luck
 Josh