Audi TT problems.

[delambo]

Right where do I start! Audi TT 1999, German import (originally rhd and not converted). My customer is a car dealer. He bought the car and had it as his demonstrator. After driving around for a while it was involved in an accident (damage to o/s/r quarter). Following the accident the petrol gauge started to misbehave. My customer took it to his Audi dealer who diagnosed the dash was faulty and scared him away with an exorbident price to fix it. I came along and verified the Audi dealer was correct in their diagnosis. I did this by reading the instrument fault codes. I then verified the fault code was correct by connecting a potentiometer in place of the sender unit, I varied the resistance and the needle didnt behave as it should have done. I then put my ohms meter in place of the gauge and moved the sender up and down, the resistance changed as expected.

I then got a new dash (from VW as they were nearly £200 cheaper than Audi) and fitted the new dash. I had lots of trouble coding the immobiliser with the new dash in (see this thread in the VAG-COM forum) so eventually stripped the dash and put the gauges from the new dash into the old one. The gauges all appeared to work fine but once the car sold the fuel gauge started to misbehave again. I went to look at the car and talk to the customer today and oddly the gauge hangs in the empty position at all times. However if you disconnect the battery then reconnect it the gauge returns to normal operation until you turn the key off and on again, at which point it hangs at the empty point again. I went into output tests and tested the gauges, all performed as they should under test situations apart from the fuel gauge which hung over empty. I disconnected and re connected the battery again and repeated the output test at which point the fuel gauge behaved itself! I checked and cleared the extensive list of codes in the instruments memory and they all cleared and none came back but the gauge continued to misbehave. I then went through all the systems and read and cleared the codes. I have never seen a car with so many faults in the memory, seriosly there must have been nearly 100 codes in the varios ecu's. After I cleared all the codes the gauge started to behave itself! I have seen cars (mostly Fiats) behave funny like this when they have been parked by power stations or under mobile phone transmittors for a long period of time, or when the car has been jump started or the battery charged without disconnecting the battery but he insists this is the case.

Hey ho, I have left him with the car and see what happens!

[jakeyfly]

Hi, does sound like you had an issue with immo 2 and immo 3 there, but saying that some 2000 cars do have that mix, and there usualy a night mare to resync.
as for your fuel gauge it sounds like a software or micro fault, me thinks you'll be seeing that one again

[morpheous]

Hi, when fitting a new dash insert on the TT, even the Centres were cought out, they changed the way the system operated for some strange reason.
You have to replace the dash and the fuel sender. If you empty the tank, you will find the gauge reads full.
Also check coding of dash is correct.