ABS activates when braking on dry pavement

CHARLES J. RATHKE

MEMBER
2007 FORD EDGE
V6
AWD
AUTOMATIC
112,000 MILES

This is my girl friends car. She told me the brakes are grinding. Checked the brake pads and the front brakes looked kind of thin and the rear pads were over half worn. Replaced all the pads and put new rotors on too. Told her okay you are good to go. She came home the next day and said the brakes are still grinding. I did not test drive it. Looked on line and found there was a lot of problems with the brake boosters on these vehicles. So I ordered a new one and put it on. Then I drove it. (I should have drove it from the beginning). Well I discovered that almost every time I stepped on the brake the ABS activated and gave me a pulsing pedal. Then I went to the scanner and found I had a problem in the l/f. I replaced both sensors in the front. Drove it and it still gave me an ABS pedal. No ABS light came on. I checked all the wiring from the ABS module and out to the sensors.I found no rubbed wires I did not ohm out all the wires. So I checked the wheel bearings and abs sensors. So I replaced the ABS module/valve body/motor assembly. That did not fix it. My last resort is to replace the ECM which includes the anti yaw and ABS processing information. My girl friend thinks this is a lot of money and wants to know if it will fix it?

1 Reply

CARADIODOC

MECHANIC
33,902 POSTS

Since you have a scanner, use it to view live sensor data during a test-drive. In particular, watch for a wheel speed sensor signal dropping out. That typically happens at lower speeds.

Since the yellow warning light is not turning on, we know there is no electrical fault, including cut wires to the wheel speed sensors, so you can forget about that. An electrical problem would be detected as soon as the ignition switch was turned on, and the yellow light would flicker off after its six-second self-test, then turn right back on again. A mechanical problem related to a speed sensor would be detected once the car is moving.

You can expect to find the cause of false activation to be something making the computer think one wheel is slowing too quickly. Look for a cracked tone ring, metal filings sticking to the magnet in a wheel speed sensor, or rust under a sensor that is pushing it away from the tone ring. There were also some Ford models that had wheel speed signal interference problems from spark plug wires routed too close to speed sensor wires. I think that applied to older trucks, but do not overlook things like that.