Q: About 2 months ago I posted a question and got some good advice, so here I am again. Very pissed off this time. Prior to replacing the clutch on my 1999 2.8 quattro 5-speed, my check engine light would come on, momentarily, if I took a hard right or left turn. It would always turn off immediately. I recently replaced the clutch (first time at 116K) and left my long-standing relationship with the local Audi dealer. Since then, the light has been on continuously. I just paid over $300 to get the O2 sensor and the coolant sensor replaced. 15 min after leaving the garage tonight, the light turned on again. Is this an incompentent mechanic? I have heard various reasons for this problem: improperly connected vacuums, catalytic converters, etc. but I need to get to the bottom of this. PLEASE HELP!!! The first code was PO140 (Bank I, Sensor II). This is the o2 sensor I believe. I don't know what the 2nd code was - they told me it was the coolant sensor. Is there anyway that the computer can read false codes, or rather that the car throws false codes? I did not have any driveability issues, or MPG reduction (which would typically suggest need for a new o2 sensor, right)?
A: If you tell me the code or codes that were stored when the light came on I can be more helpful. There are hundreds of reasons for the CEL to come on & the codes are a starting point for diagnostics.