Was hoping it was just the sensor, but no, my mechanic thinks the ABS is not communicating with the computer. He tested the connection all the way back and thinks the computer is the problem. Any other possibilities I should explore before trying to find a new brain (somewhere, maybe Greensales?)?

 

I'm talking about the rear ABS on the 1989 F-250 naturally.

 

Best bet is probably to check for trouble codes. Look under the dash, above the parking brake pedal for a black/orange wire with a single connector. With the key on and the ABS light on solid, momentarily ground the black/orange wire, the ABS light should now blink out either a single digit or a two digit code.

 

There is also a ground connection that the ABS needs, it should be on the front of the engine compartment near the wiper fluid container. Also very close to the radiator cap. Near that area you should see a ground connection. If that connection is not correct for whatever reason, the ABS will freak out (happened to me).

 

Does your spedo work? Your truck should use the same sensor for both, and splits the signal with the a module. Just another point to fail. Something to bring up with your mechanic (they cant/dont know everything). If the spedo works, not the sensor, and might not be the signal spliter. Then there's the ABS module itself and associated circuitry, and if I remember correctly this is all completely independent of the engine computer.
-Mike

 

Man just get in your manual, and find the ABS fuse. If the fuse is good, then check all your connectors for corrosion. And FYI there may be two ABS fuses one under the hood, and one in the fuse panel. Dont ask why, but I have seen it more than once.