0171, 0174, System Too Lean, Which Senosors to Replace
 

Hi folks...new to the Audi world with a 2001 A8L, 4.2 Liter, 44K miles. Car is beautiful and runs great but it throws 0171 and 0174 "system too lean" codes. Question is where to head first...oxygen sensors, Mass Air Flow meter, or something else. I figure many of you seasoned veterans out there must have some experience on this.

Also, I have shareware version of Ross-Tech Vag-Com but am pretty new to using it. Can it (or it's fully registered version) actually diagnose this down to the sensor? I'd be willing to lay down the license fee if it does the job.

Thanks for any help...

16555
P0171
Fuel Trim,Bank1 System too Lean
16558
P0174
Fuel Trim,Bank2 System too Lean

First check for any vacuum leaks, it will probably be a large leak with these codes.
If you can't find anything wrong with those, it would most likely be a MAF sensor. The regular version of the vag com can diagnose it, you just have to understand the data blocks. Look at the MAF data while driving, if its out of spec then you know the problem.
I would also remove the electrical connector to the MAF and see how it runs.

Try to keep it to one thread... you now have the same answer twice and it makes it hard to follow what was already done :)

Thanks for help
 

Thanks for the great tips. I had already found and repaired 1 vacuum line but will look again. Will also try the MAF dosconnect and observe.

Thanks again

As for multiple postings, sorry... New to this game and unsure where to post. The A8 Forum appeared to be dead (last posting was in April). I got a few reads but no replies. But I promise to stick with one forum. Thanks for the heads up.