Hello,

Can anyone help with diagnosis (or procedures for diagnosing) a 92 Cherokee that begins to brake at highway speeds without touching the brake pedal. Brake hardware seems ok. I assume ABS but, I don't know where to begin for a diagnosis. Computer fault code does not register a fault. I appreciate any help anyone can give.

Thanks.

 

ABS couldn't cause that, all it does is restrict or stop fluid going to the wheel cylinders, it can never create pressure itself. By braking do you mean a wheel locks up or just starts gently slowing down?

 

The ABS engages as if the car were on a slippery road. The actual road conditions are: traveling over 55mph over a patch of bumpy, rough or potholed road. It appears that the sensing system thinks these conditions are more severe loss of traction and the anti-lock braking behavior starts - with a gradual slow-down due to anti-lock behavior of the brakes engaging in a flutter as they should - on slick roads.

 

Tires all the same size? Worn front hubs/bearings, bad wheel sensors....

 

I vote bad sensor. Mine's been doing this at low speed for over a year, but I'm confident enough in my ability to stop quickly without ABS so i just pulled all the fuses and relays for it. Have plans to remove it completely.

 

Thanks for your thoughts. I'll try the sensors first - bearings next. Tires are all the same size. Thanks again.