brake

I have a 1995 G20. Recently while driving the Tach was jumping for a little while, then recently, stepped on the brakes, got a 'scraping' noise, the pedal pulsed, the speedometer stopped working, and check engine light came on. Drove home and shut off car. Restarted - brakes seem fine, check...

couple of odd things going on with the brakes: 1) if you apply the parking brake the abs light comes on 2) have low pedal, but if you pump it up it gets firm. the master cylinder diagnosis was good, so its not that. there are no leaks, system was properly bleed and pads are excellent. please...