have 2004 a6 3.0. 25,000 miles on it. My check engine light came on. Turns out its speedsensor on diagnostic check from discount auto parts. Car is still under warranty. Problem is everytime i go for a schedule appointment at dealer the light turns off. I can not tell any difference in driving. If there is a difference its prob very small. I am getting tired of briging it over to dealer and light turns off (leaving nothing for dealer to look at, codes dont store). Anyone else have this problem. Also, should I be worried about driving around like this even though i cant tell any difference ( dont wanna cause damage)

thanks, any advice is great

 

could be the wiring plug on the speed sensor come loose, the light will only come on when there is a fault or loss of connection in the system. try looking at the plug and also that the sensor is fixed securly down. Dont sound serious as its not on all time. if there was a abs, esp fault it would be stored in ecu memory.

 

anyone know how to locate the speed sensore on a 2004 a6 3.0l

 

Actually the code will store as a sporatic fault in the individual module, if you check the OBD log it will only have a fault if the check engine light is on like with a autozone scan tool that can't read the individual modules. The audi factory scan tool should almost always be able to read a fault, even if the light isn't on.
Not to mention it could be either and engine speed sensor, trans speed sensor, wheel speed sensors ect you don't even know which speed sensor is faulty.

 

true, true, find someone with a Vag com scan tool and you'll be able to scan the individual modules, which it should have that sporatic fault stored in there. definitely cheaper than taking it to the dealership, but since you're still under warranty i suppose it doesn't really matter.