jeffkruse

Sorry if these questions seem stupid but I am no mechanic. The dealership I purchased the 2004 Audi A8 put 87 octane gas instead of 91. Would that throw P0171 and P0174 error codes. He said the check engine light was not on when he drove the car back from the auction but he put after he put gas in it the check engine light came on and he put the computer/machine and it threw those codes. I also had Autozone run a diagnostic and it returned the same codes. Secondly the washers for the headlights work for the drivers headlight but does not even open for the passenger. Please advise, thanks.

jamm220

First off sorry your first a8 experience started this way. I am dealer and in our state a dealer cannot sell a car that doesn't pass emissions which more than likely in your case they car wouldn't due to those codes. Not sure the rules where you live or even if you do the smog test . The AutoZone readers are just there to kinda guide you and give you and idea where to start. Find someone with a vag or buy it you will need it. As for the headlamp washer it could be several things but vag will scan that too maybe the motor dead

mishar

You should buy VCDS (VAG-COM). It will pay itself in a no time. Scan will tell you (and us if you post it here) much more than those codes.

Washer wise, check the connection first. There are same harnesses for the washer lift motor and side marker light. Something may be mixed there. To reach that area take the wheel and the front part of the wheel liner off. You may first try to reach trough fog light grill. Just pull it off.

Mister Bally

P0174 could be from a loose fuel cap, but not P0171.

I have used 87 octane for about 175,000 miles on my '04 and do not have that problem.

Albatrossboss

In terms of the codes, I'm of no help there, but when I purchased my 2005, the headlight washers didn't work, Mishar suggests taking the wheel liner off, but I just dropped the belly pan off and looked with a flashlight. Sure enough the hoses weren't connected on the Passenger side and the nozzle had fallen out of the bottom of the Driver side. I bought some plastic epoxy that is made for watercraft and can set underwater and reattached the nozzle to the housing beneath. If you need more info just PM me and I can forward photos of what I'm talking about in more detail.

MP4.2+6.0

1. As stated, get VAG COM/VCDS. Those P codes are low quality info, and makes helping harder. Also, you will get better responses if you post the description you can get for any P code just by googling. We don't have those memorized, so readers often have to Google...or skip.

2. Having Googled, those look like lean codes. Most common there are vacuum hoses or the secondary air injection system. And no I will be clear from a prior overlapping post. This didn't just "happen" and leprechauns didn't just dance on the hood either. Absent incredible coincidence, someone in the distribution chain most likely took a $50 code reader you could stuff in your pocket and in about 10 seconds cleared the codes and the CEL. Really unethical (frankly likely fraud if done with intent to mislead and for commercial benefit), but seems to be happening. Cars that don't pass a smog test can't be sold here in CA, and if you know what you are doing with a VCDS you can also read the "readiness" codes to see if someone just tampered with the car by clearing the codes without a repair. And with the lean codes, it usually takes two cold-hot-cold engine cycles for them to appear, so codes were cleared a few cycles ago, not 10 minutes before you showed up.

3. On washer, again you need a better tool to narrow it down. On mine, shortly after I got it I noticed one side sprayed a couple of seconds before the other. At first I thought it might even be some German stereotype precision feature. Dealer diagnosed it as some kind of bad relay or switch. Each side is apparently separately controlled instead of flowing through only one valve/switch.

mishar

If it is same as 4.2 and I don't see any reason why it won't be, than there is a single relay and single pump for both sprayers. Two jet motors of course. They also rise and spray at the same time here. Hose is coming from the right side, to the right sprayer first and than to the left one. I believe if there is a small leak in that hose going from the right to the left side it can create an air bubble causing a small delay. Those hoses are unbelievably brittle.

Albatrossboss

Doesn't the D3 share some engineering ideas and other things with the Phaeton? I was watching the Top Gear piece on the Phaeton and they said that the headlight washers come on at different times so the driver always has at least some clean light on the road (Autobahn safety comes to mind as a possible reason).

Albatrossboss

This is the piece I'm referring to. The headlamp info is at the 3:20 mark

MP4.2+6.0

when I first got it, something triggered me to look at it. I think there may have been a code. Anyway, you pulled on wiper stalk with lights on, and at 2 seconds it hit drivers side headlight at full spray power. Then after about two more seconds it hit the passenger side, also at seemingly full intensity. No apparent leaks. Post the work (I still probably have work order order somewhere) they have always sprayed together.