Had some previous discussion on this. ABS light on permanently. Brake light intermittent. While fixing another electrical problem, I had all speed sensors cleaned and brake sensors (wire) checked. Diagnostic faults front left speed sensor - signal implausible (code 21 or 25, can't remember). Also cleaned the two relays in the front just above the spare tire.

Looks like I'll need to replace the speed sensor - any suggestions on a good supplier, and do you recommend an aftermarket sensor or should I stick with OEM?

The question I have, which seems to have been implied with some other posts, is can a faulty speed sensor also cause the brake light to illuminate intermittently? I thought the speed sensor had nothing to do with the brake light.

Thanks for your assistance.

Kurt

 

I had same problem (albeit on my 964) Turns out the wiring from the car to the connector block for the speed sensor and brake pad indicator was bad..

 

Thanks, Silvertarga. I'll check that out as well.

Kurt

 

I had the issue with the abs light before I switched my brake sensor wires out. As the pp said, check these.

 

is there a way to test the wires? just use continuity? from sensor to ...?

 

There is a resistance test for the sensor, you might want to check it vs. the other ones. Or swap it over to the other side and see if the problem follows.

I would go OEM on the sensor, they are not expensive.

 

Thanks Stealth

 

Check the relays in the trunk. Also I had this issue until I forced the ABS to go active through a hard stop. This settled the issue and I never saw it again, go figure?