Hello all. This will be my first post. Here goes. I just bought a 1993 100CS Quattro Avant for a fair price, expecting some maintenance. I have owned lots of VWs and a 1990 Model 90 in the past. This car has numerous issues that all will be addressed in due time, but foremost is the CEL. Its kicking a CEL after anywhere from 5 to 25 miles after driving (warmup). Also, after another 5 minutes or so, my door chime or some other buzzing indicator comes on and persists to no end. I've only had it a few days and I see the storm clouds a comin'. The car does run fine however, very smooth.The radiator fans run constantly, the oil pressure is darn near pegged, and the heat gauge only moves marginally . Also there appears to be the start of a high induction K&N project, with a suspiscious wire spliced into the MAF. Should I grab my ankles and brace myself? First things first I guess. I've received some decent tech forms through Alldata on how to make my own LED diagnostic tool. I am mainly wondering if anyone has had experience doing this, preferably successfully. I nuked a Subaru ECU once, I would HATE to pop my Audi's. I cannot afford to go to the dealer, simple and true. I will do this myself or bust. There is also the carpet-bombing of parts approach. I could just replace all the usual suspects like O2 sensors, temp sensors, oil pressure sensors. Does that approach offend the tried and true troubleshooters here? I could do it and call it routine maintenance, but wouldn't codes be more, eh, sophisticated? Any help is greatly appreciated, the buzzer is driving me nuts. Many thanks to the hosts and Admins out there that make this gold mine of a resource work.

 

For the CIS cars I have used a test light from sjmautotechnik.com don't know if it will work for later models. My general experience with older high mileage vehicles is corroded electrical contacts.