I am new so I am sorry if this is in the wrong spot. I have searched but haven't found any old threads like this. I have a 2000 Audi A6 2.7t quattro. I just bought this car last week. The check engine light is on and the guy I bought it from (he is a friend) said that the Audi dealership said it is because the aftermarket stereo wasn't installed right. I tried pulling codes from going to checker, but the machine wouldn't pull the codes. I have read on here that the A6 uses a different system, but the guy who pulled my codes used to have the exact same year/make/model. In other words I am wondering if I should pull out the stereo and check the wiring. Has anyone heard of this issue?

 

Any OBD II reader will read most of CEL codes. There are some Audi specific codes, which can be read by VAGcom but if your CEL is on, any reader will read the trouble code. I somewhat doubt the aftermarket stereo will trigger a CEL.

 

Ok so I took my car to an Audi mechanic. He said that he has seen this multiple times. When the previous owner installed the stereo he plugged in a wrong wire. There is a wire that goes from the computer to the stock stereo. Apparently when rewiring you are supposed to leave it out.