I have a 01 1.8t 5 speed with 99,800 miles and my code of p0171b just came up. I'm not sure why it came up as bank 2 because its a 4 cly.My friend cleared the code, and it came up again after 15 miles of driving. Any help on this one guys? Is it safe to drive? How much would it be to fix, and where is this part that might be broken located? I'm new to the Audi and awd drive world, so any advice about the car would be greatly appreciated!

 

P0171 Fuel Trim, Bank 1 System too Lean

Check for vacuum leaks.

 

i checked all my vacuum hoses with some starter fluid while the car idled, and at no point in time did that car idle jump or drop.......any other ideas???

 

yes.. Your problem most likely is the mass air flow sensor. You need a new one. And also when you buy it make sure it isn't refurbished, it needs to be brand new. Put that in and the code will go away after about 70 miles. You can trust me on this one... I had a year long problem with that code. And after reading all these posts and checking absolutely everything.. that was the problem. If it isn't, check vac leaks up in intake manifold. The two oxygen sensors, fuel filter and fuel pump. but I'll put my money on the maf

 

http://wiki.ross-tech.com/index.php/16555/P0171/000369

 

Is there anyway to test the MAS to see if it is defective, or is this going to be like a 130$ gamble on a part? lol I'm not cheap but i would rather work with finding out exactly what the issue is before i buy a part. Thank you guys for everything! Its helped me out greatly!

 

well are you handy with a dvom?? you need to find the signal to ecu return.. find out how many volts you should be getting at idle on that wire, and see if its with in spec. then you can also see what it should be reading at a higher rpm and such.. just make sure that it stays within spec. with these symptoms you probably will not see any glitches.. just a degraded miss reading sensor..

 

Yes! $130 dollars is a good cost for a brand new MAS. Get it! Im almost one hundred percent sure that's your problem. And it's a cheap and easy one compared to most fixes with Audi's!!! Put it in... located on left side of engine on top of the air filter or behind it depending on year. Give your computer about 70 miles to program it.. and your light will turn off!!! This is a BIG "bank 1" problem and that's why Im sure it's your MAS. Besides, you usually need a new one every 70 to 90,000 miles... so your OVERDUE!

 

And yes you can test your mass air flow sensor with a VAGCOM. If you dont have access to one, take it to a european mechanic and they should be able to test it for you. I can't tell you what readings to look for.. listen to BIGERN45 about that one. But that will tell you or a mechanic exactly where your misfires are coming from