Markgcb1

I replaced my MAF with a new one from Audi because I had Autozone scan my car because the check engine light came on. The code that came up was 16555 P0171 Fuel Trim - System Lean (Bank 1). Most of the replies I got from this forum and others as well as the tech's at the dealership stated it was th mass air flow sensor. I had my mechanic replace it with the new one and he turned off the check engine light. Two days later the light is on again. I scanned it again and the same code came up. Does anyone think the problem is something else or do I have to drive the car for a few miles before the check engine light will go out all together? Does anyone recommend possibly using a fuel injection cleaner? If so what brand? THanks in advanc e for your help.

TTschwing

Disconnect the Neg terminal on the Battery for a few minutes and you'll start fresh. It will correct itself as things adapt in a few miles, but a re-set will hasten things along. If you stll have a Cel you may have a vacuum leak or Bad 02 sensor resulting in a lean condition..

Markgcb1

Thanks for replying TTschwing/Modshack. How can I check for vacuum leaks and bad 02 sensor? What are the symptoms for booth? What is the cost generally for an 02 sensor or a vacuum leak? Does disconnecting the neg terminal on my battery work better than just have the code erased by autozone or anyone that has a obd diagnostiuc scanner? Thanks agian for your help.

TTschwing

and erasing the codes doesn't reset them. You have to power down the system.

Deal with this first. YOu nee some VAG diagnostic gear to find faults. Vacuum leak will throw a lean code and give you erratic idling sometimes. Without a boost gauge, you're just guessing though..

Markgcb1

Okay thanks, I'm not a mechanic but I will try to do what you mentioned first by disconnecting the neg terminal for a few minutes. How can I get VAG software and equipment? I can tell you that the first time I had this problem the car started idleling rough as I sat at a stop light, the next day the CEL came on. Then after I refueled the gas tank, the light went off two days later. It then stayed off for a few weeks, then came back on that's when I replaced the MAF. I was under the impression that a bad MAF will also throw a lean code and give you erratic idling sometimes. Am I right? Is vacuum leak expensive to fix? Does the vacuum leak come from a hose? If so what hose? What about 02 sensor is it an expensive fix? The car runs great now, so I just trying to figure out what the problem may be before I take it to the stealership and get beat!

TTschwing

<ul><li><a href="http://www.ross-tech.com">Vag Com here..</a></li></ul>