Hi all,

I own a 2003 Audi A4 1.8T with 90,000km on it. Last week I got the timing belt and water pump replaced at a dealership. Last two days I noted a lack of acceleration on the car. While idling the car would some times idled higher and sometimes lower and was erratic. Some one suggested high Octane fuel so I put in sunoco ultra 94 Octane fuel over 1/2 tank 91 Octane ESSO fuel that I had. After about two km's check engine light came on.

I got the codes read and these are

4 tdc found

18062 - Check TDC memory of Instrument cluster P1654 - 004 No signal/communication - Interm

17519 - Oxygen (lambola) sensor regulation bank 1. system too lean.

16891 - Idle control system RPM: higher than expected. P0507 -001 upper limit exceeded.

17544 - Fuel trim bank 1 system too lean P1136 -001-Upper limit exceeded - Mil ON

The garage is not sure about the first code but is sure that two of these codes are due to Vaccum leak and is checking for one.

Please let me know if anyone came across such problem and resolutions.

 

I searched on AZ for a bit, nothing really helpfull, but it seems like it might come up with the system running pretty lean --- thats your case.
Try cleaning your MAF sensor first with MAF CLEANER SPRAY. Then open your hood and listen if you hear any air sucking in sound.

 

the first looks like a bad cluster or a bad connection to the cluster.

the other three are deff lean codes, like your mech said, prob due to a vac leak.

 

I also have had a very hard time with codes being properly diagnosed and fixed correctly. If you check my posting history, you'll see I also went through hell trying to fix my Audi.

I don't know what's wrong with your car, but I will say PLEASE, do NOT take it to your Audi dealer. They jerked me around telling me I needed a $4300 repair, when they were actually wrong, and my repair cost less than $1000.

Point being, find a GOOD independant mechanic. One that KNOWS what he's doing. That's what someone on this wonderful forum suggested, and after a couple tries, I found a good one. I suggest some local who specializes in foreign cars. Worth their weight in gold.

BTW, does ANYONE know how to change a headlight (Driver's side) on an Audi A6, 2002?? The dash light is one, and the light is out. Thanks. (Yes, I did search this forum, but there were no pics, or detailed instructions. I don't have the halogen bulbs, so it should be safe to change myself. I hope. LOL

 

I would clear all the codes then check them again in a day or two to see which one comes back immediately and start there.

The O2 sensor is something to keep in the back of your mind and maybe some new plugs or even trying the seafoam DIY.

 

if you think about this all your codes lead back to the first code of 18062 - Check TDC memory of Instrument cluster P1654 - 004 No signal/communication - Interm

Interm is intermittant
so in theory you would have misfires which would lead to too lean causing your O2 sensor to come on. if you did not know when your TDC(Top Dead Center) was on the vehicle how can it know when to fire?? bring the car back to the fools that did the timing belt and pump they messed it up and they better fix it also. i might have even skipped a tooth get it check out from the fools that fixed it man

 

a 2002 A6... its very possible your in need of expensive repairs... especially if its a 2.7, especially if its over 70,000 miles.