Hi All,
I have a 2001 A4, 1.8T and the CEL has recently illuminated. I have checked the code and it is P0171 "SYSTEM LEAN, BANK ONE". Does anyone have a clue where I should start looking in order to fix this? I don't know if it is a common code, but any advice would be wonderful.
Thanks

 

intake exhaust leak, air system, vacuum leak im going for an air leak in the pipes

 

Dave, you mean a vacuum leak?

 

i had the same code last year. It turned out to be a simple hose/line going from the top of the intake manifold. Check if any hoses are frayed/cracked....

 

Thats great guys. Thanks for the information. I'll be looking for a leak in the vacuum hoses tonight.

Neil M.

 

anything that's breaks the air/vacuum is considered a leak ( lost pressure in the system ) causing a lean running condition, fault codes are only a guide

 

Okay, I found a split vacuum hose, the one at the front of the intake manifold, probably the same one as a previous poster mentioned. I have repaired this so I'll see tomorrow if the CEL comes on again. The vacuum hose was so brittle and rotten, that I would imagine they must all be in bad shape, but that was the only one that I could find a problem with.I will probably change them all when time permits.

Thanks again for the advice.
Neil M.