Driving towards a stoplight and the brake pedal went to the floor on a 1996 Buick Century. Pumping gave only partial rear braking. Drove to friend's house (during which the brakes worked normally the whole way). We pulled the driver side tire and discovered that the fibrous finely woven tube cover (fiberglass?) to the extremely thin and fragile wires to ABS sensor looked burnt. Cutting it off we discovered the wires inside had shorted out. When we cleared the short and individually wrap insulated the wires, the ABS warning light then came on. A gravel skid test revealed no ABS at all. We found that dead shorting the wire to the sensor with a jumper wire will cause the ABS warning light to go out, but obviously disables the ABS. We replaced the sensor (which requires that the whole bearing/stud assembly to be replaced), and then the ABS light went out. A gravel skid test revealed the ABS working fine and he says the normal braking is now better too. Some research reveals that the ABS detects no tire turning during a skid via the sensor, and releases hydraulic pressure to the brakes until the tire is detected by the ABS as turning. We think that when a short to the sensor occurs, the sensor can't detect the tire turning again and thus the ABS unit never stops bleeding fluid pass the brake (and the initial short may even set off the ABS without an actual skid occurring - that is without the sensor ever sensing a tire not turning). Anyone having random near-total or total loss of brakes on this type of vehicle might do well to examine the wires and terminals leading to the ABS sensors - and replace suspicious units (we paid about $90 for a unit from a common auto parts chain). A gravel skid test might also reveal an ABS system not working even though there is no ABS warning light lit. Replacing the bearing/stud/ABS sensor assembly is moderately hard.

- Dravosburg, PA, USA