I have a issue with a 2003 A8 that is kind of different.

The symptoms are:

When the headlights are off:

Light warning/ warning chime when I push the brake pedal.

Goes away after brakes are released. I did notice that the front running lights glow brigter when I push the pedal.


When the Headlights are on:

Unhappy Triad Condition - BRAKE LIGHT / EBS / ABS

Goes away after you restart the vehicle with the headlights out.

I think also that the Brake lights are dimmer than normal.


The Ross diagnostic tool reads a Brake Light Switch code, but drilling down deeper, I can see both poles of the switch
pulling in when I press the pedal


This sounds like a bad ground to me. Does that make sense?

Has anyone seen this one?

Does anyone know Where physically the lighting system grounded in this car?

Can this be caused by bad lamp connection(s) ?



Thanks for your help!!!

Joe

 

I just had the same problem ebs and abs would come on. So we replaced the brake light switch. Also there was one bulb going bad. It was out and when I went to take it out the light came back on. I left the bulb in and kept getting the brake light popping up. After 1 week of going crazy I decided to change that bulb that came back on. And it it solved the brake light problem. Sometimes audi are real sensative.

 

I found the problem!!

What happened is that one of the tail lights failed, sorta.

The brake light filament was shorted to the tail light filament, probably due to vibration over time. When the Tail light was tuned on, the +12 back fed into the line side of the brake light circuit, causing all of these weird symptoms.

It's always something weird like this that gets me.

Joe