94 Cutlass Ciera S Brake and traction light
 

1994 Oldsmobile Cutlass Ciera S 2.2L 3 speed automatic. 4 door with ABS. Milage about 184,000
The problem I am having is that the Brake light and Traction low lights are "on". I say "on" in quoted because they are more like rapidly flickering than steady on. When I apply the parking brake the brake light gets brighter and becomes steady. The Traction low light stays flickering.
I bled the brakes in hopes that would fix the problem. I did a test on the vacuum booster and it passed the peddle drop test and the vacuum release test. The brakes feel a little spongy but still function. All 4 are working (got it up to 30 mph and locked up all 4 wheels with out any problem). Obviously the ABS is not working. The strange thing is that there is no sounds of vacuum leak. The engine starts and runs fine and idles smoothly. The brake and traction low light stay "flickering" until at highway speed the engine is under minimal load. then both lights go out. Acceleration will bring them on again and slowing down will also bring them on again. Of course the brake fluid is full. Im wondering if I have missed something in the booster or should I just go ahead and rebuild the master cylinder?

Update: did some checking. Could it also be a faulty Brake Pressure Warning Sensor? I cant seem to find one in any parts listing but the manual says you have to remove one to rebuild the Master Cylinder... Any one know what part number that would be?

UPdate: Master Cylinder rebuild was a success but problem remains even after all lines bled. This narrows it down to a failed ABS Valve Module :(

Hear a humming noise when you turn the steering from left to right at 25mph? Could be a speed sensor or wheel bearing .