this sounds ridiculouse but i had the same problem.i hadnt washed my car for ages so washed it and jet washed the wheels to get all the old brake dust out and it worked.
john redmond
October 2007
The problem could be a couple of things, sensor, computer, brake proportioning valve. Best thing is to get a manual on the car and do some test it suggests, to find out what is wrong. My vehicle was a speed sensor that went bad, I put a new one in and it fixed it. But, you still have to get the code erased or it will still be on.
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Try fixfault.com to fix cars.