Quick Question

[A4_luke]

I have the CEL light on my 1999 audi a4 1.8t quattro with code P0171 running lean. I took out the maf sensor and cleaned it with maf cleaner. my question is should the CEL turn off after driving for a lilttle while or do i have to get it reset? if not i guess my next step is checking the vac lines

[Seerlah]

You will have to clear the CEL via Vag Com or OBD II Scanner Tool (Autozone lets you use thiers for free). The CEL will not disapear on it's own.

[A4_luke]

okay i guess ill stop by autozone after work and clear it than go from there if it comes back. thanks for the reply

[zrowcool]

you can disconnect the battery and reset the ecu by putting the positive and negative terminals together for 30 secs. MAKE SURE THEY ARE DISCONNECTED!!

[Seerlah]

To the OP, if you decide to go that route make sure you do the throttle body adapt before you start the car back up. To do a throttle body adapt, you place the key in the ignition and turn it to the last slot but do not crank it (all lights on cluster will be luminated). Let the throttle body adapt in this position for ~5min. If you do not do this, when you crank the car your idle will be everywhere. Also getting the radio code might be a good investment (but I removed my battery maybe 5 times already and have yet to need to re-enter the code).

[A4_luke]

I think i ll play it safe and jus get it reset i dont have the radio code and its 5 minutes to autozone

[A4_luke]

I just hope this fixes the problem. the car drives fine idle is good everything drives like it should i really have no idea why the CEL is on. hopefully this does the trick

[Seerlah]

Oh, I thought you already knew why you had the CEL. You should use the scanner, get the codes (CEL is there for a reason), then clear them. If you do not fix what the CEL is there for, it will eventually reapear again till the issue is resolved. You can look up the codes at http://wiki.ross-tech.com/index.php/...ry:Fault_Codes

[flynnr]

i have the same code just thrown... :\ i think that i might have a vac leak like you said... where are common places to look for this or how do i do this?

also - will this make my car any slower or anything? it doesnt seem any different yet

[Seerlah]

This is what Ross-Tech says:

16555/P0171/000369 - Fuel Trim; Bank 1: System Too Lean
Possible Causes
Mass Air Flow Sensor (G70) defective

Possible Solutions
Check Mass Air Flow Sensor (G70)

Check Fuel Pressure Regulation

Check Fuel Pump

Check Injectors

Check Intake System for Leaks

Check Exhaust System for Leaks

Check Secondary Air System for Leaks

Check Vacuum Pipes for Leaks

MAFs are not cheap. And if that is the issue, there is no reason why not to get a used one for ~$50 used if it is still in good operating condition. I actually sold an extra one I had laying around a couple days ago for around the same price. But you should do a boost leak test to fix any leaks, if you have any. Plus check all hoses and clamps associated with the intercooler/dv. Those are prone to coming loose and causing greif to B5 owners. The link provided is the technique I use for my boost leak tests, which I perform periodically for good precaution. http://www.a4mods.com/index.php?page...boostleak.html

[A4_luke]

i cleaned the maf sensor today got the car checked again got the CEL reset came back after a couple miles code is - P1136...thanks for the reply seerlah i am gonna check the vaccum pipes tomrrows

[Seerlah]

People check thier MAFs by logging it with a VAG Com. Where in Jersey are you located? I have a VAG Com and can log your MAF for you if you want (taken you are close to my residence. or another can assist as there are many freindly people on Audizine). But more than likely, that seems to be the issue. Those things tend to go on our vehicles.

How did you clean your MAF? You should use CRC MAF cleaner found at Autozone. I am about 85% posotive it is your MAF.

Edit: I found an AEB MAF being sold in the classified. http://www.audizine.com/classifieds/...t=3500&cat=all That is a good price for it. And the person selling it is a well respected person in the B5 A4 section, so there should be no issues with the transaction. Send him a PM (private message) if you are interested.

[A4_luke]

i ended up doing a pressure test and found a cracked check valve and a broken hose i fixed both and reset the code put its back on now giving me p1136