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Tech Article

Audi C5 A6 Yellow Brake Wear Warning Light

Last Updated: 04/03/2017
Parts Group: Instrument cluster
This article discusses the yellow brake warning as can appear on the liquid crystal display at the top center of the rectangle in the center of the instrument cluster. The display shows a circle with a crescent on either side.

This warning is displaying in my 2000 Audi A6 Quattro 4.2 V8. I know from personal experience that there is an electrical brake wear sensor on the front brakes. I checked the front brakes, and the front brake pad thickness seems fine. So, that meant either a problem in the wiring, or a problem with the rear brake pads.

My tech and I jacked up the rear of the car and removed the wheels, then checked the rear brake pad thickness; it's within tolerance, as in: it has probably more than 25% to go. More importantly for our quest, we didn't see any electrical connections on the rear brakes, as to brake wear sensors. So, that means the wiring is suspect.

On some of the more-humble cars I've owned, there is a brake wear sensor on only one front brake, the premise being that if one side is worn then the other side is probably equally worn, so monitoring only one side is good enough. Audi disagrees, and monitors both front brakes for wear.

I haven't yet verified this personally, but from some reading I've done, I gather that the circuit runs from the instrument cluster to a connector, then the brake wear sensor on the driver side front brake, then back to another connector, then the brake wear sensor on the passenger side front brake, then to a connector, then to a generic ground connection.
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