ajg617

Had the timing belt done on Monday - car ran great and still does. On an errand tonight, the CEL comes on. I pulled the codes and after reading some of the posts on the forum, I'm kind of hoping it is all just a loose vacuum hose. I have Bentley for my daughter's A4, but not for my A6 (2003 Avant 3.0 with 94,800). Drove about 50 miles since timing belt and have not put any gas in. Any help would be appreciated.

radhaz

Helpful resource:
http://wiki.ross-tech.com/index.php/...ry:Fault_Codes

socalclimber

I have eBahn repair manual and when checking codes for 2003 A6 Avant w/ AVK engine, I get this info for first 2 codes, but can't find anything on 1857.

SAE VAG Description
--- --- -----------
P0421 16805 Warm Up Catalyst Efficiency Below Threshold Bank 1
P0441 16825 Evaporative Emission System Incorrect Purge Flow

There are details and what to check on these, but I don't know if I can copy all of the procedures easily enough to post.

P0421 goes into checking O2 sensor heaters, before and after Cats, make sure engine control fuses are all okay. If O2 sensor doesn't get + voltage for heater, it will be sluggish and throw a code. Checks all O2 plugin connectors and where they go to near firewall--maybe 1 is loose or disconnected when TB was serviced, or coincidence?

P0441 goes into checking EVAP canister for proper seal, and checking N80 purge valve function. Checking vacuum lines is a first step, esp. near EVAP canister.

Let me know if you want me to outline some details of the procedures. Do you have a volt-ohm meter and know how to use it to measure voltage and resistance?

Good luck.

ajg617

I do have an ohm-meter (going to replace batteries first). Can you tell me where the EVAP canister is on this beast? Also does your eBahn manual say anything about ECU flash upgrades for AVK? I know there were some for some 2.7s - not sure about the 3.0 though?

Looks like the code that set the MIL was the 16805.

socalclimber

Before going further, take off gas cap, moisten seal a bit, and tighten until it clicks--maybe you're getting some vacuum loss here--this can set your check engine light too. Drive somewhere for 15 min and see if that helps. Check obvious vac lines in engine compartment. Get the good German vacuum hose, not the American crap. If no, keep checking, read on.

My Bently service manual (hardcopy) says EVAP canister is in bottom of spare tire well under a cover. There are MANY vac lines in the area to/from fuel tank. There is also a fuse for N80 EVAP purge valve in fuse panel...might want to check all your engine fuses, and O2 heater + wires have a fuse as well at panel.

The fuel overflow reservoir and associated valves are in the rear of the right rear fender, behind the wheel housing liner. The leak detection pump is under the front of the same fender.

The O2 cables and heater connectors are on each side of engine compartment at firewall in rear of engine compartment. Left (drivers) side connectors under coolant exapnsion tank.

I will work on posting some diagrams and procedures soon. There's a lot of them, and I found a mistake in the Bentley service manual--they posted the wrong diagram for the 1998-2004 V6 3.0 Engine management layout items 1-16, so I don't have that.

Cheers.

socalclimber

ajg617,

The only way I can figure out to post procedures is to print them, then scan to PDF, and there is 15 pages for fuel evap testing and 25+ pages for O2 sesor testing, etc.

Let me know if you really want and need them. Did you check your gas cap, then drive around a bit, and check obvious vac lines in engine compartment?
~socalclimber

ajg617

Thanks for all of your help. Gas cap seems OK, but will moisten the seal a bit this morning (have to pick up pads and rotors for it to get through inspection). I'll check fuses before I go - then might take a ride over to the mech who did the belt and see what he has to say. I have to pick up my daughter's A4 there anyway.

Took a cursory look in the engine compartment and didn't see anything hanging off or disconnected. Everything looks tight. Audi tells me there are no flash upgrades for this vehicle, Soooo... I'll play with it a bit today and get into some more serious testing tomorrow.

ajg617

And of course yesterday morning, I went out started the car and the CEL went off. Happy about that.

Redneck Truck

I'd check for loose grounds and low battery if it flares back up again. Those problems seem unrelated and, when occurring in such close proximity to a service, lead me to believe the service may have caused them. Anyway, glad it's fixed.