ABS engages for no reason

[nrschaaf]

For a few months my ABS has kicked in for no aparent reason from time to time. It happens on dry roads, wet roads, on and off dirt. I have found the only common thing is it seems to only do it at low speeds, bellow 20 MPH. I had my local mechanic look at it but it won't do it while hes driving. Any thoughts?

I tried searching other problems and couldnt find one like this, if anyone knows of a thread already addressing this I'd love to check it out. Thanks

 

[XLT]

I wonder if it's not related to the abs wheel speed sensor. My truck's abs use to kick in when i was coming to a stop, and would make me overshoot my mark by a good 10-15 feet becuase of the abs kicking in everytime. I saw the price ($100+) of a new abs sensor, and never raplaced it. I just pulled the fuse for the abs and "solved" my problem. When you say low speeds are you talking about coming to a stop? Kind of like i described with my truck or different?

 

[nrschaaf]

Yeah, or if I'm on a steep road trying to maintain a crawl on the brake it'll do it too. Do you know if this truck have 4 independant sensors or 1 per axle? I suppose it's probably too old for the dealers computer to read ABS issues right?

 

[IZwack]

Check tire pressures and make sure all tires are worn down to the same level as tires of varying diameters will be interpreted as a slip.

 

[XLT]

Check tire pressures and make sure all tires are worn down to the same level as tires of varying diameters will be interpreted as a slip.

That is some really good information. I totally missed that he has awd.

 

[nrschaaf]

Yeah, the tires all have the same air. The tires on there now have under 1K on them. It did it with both sets. It is great info though, the old tires were completely shot, and i know for a fact werent worn evenly. Could the ABS need time to adjust to the new tires? I went with 31x10.50x15 with this set instead of stock. Maybe a calibration issue?

 

[my98nnj]

Per mature abs activation usually means a sensor is losing its signal indicating wheel lock up to the abs controller. There are 3 sensors in our trucks, 1 on the rear on top of the pumpkin and 1 on each front wheel hub. Consider cleaning them as debris tends to build up on the sensors over time. Check their resistance while you have them out as well. Make sure they are all within spec after they are cleaned up.

 

[jakemccarthy]

I would just put in a kill switch if I were you.

 

[kevinspann]

Checked for cracked ABS tone rings, or a ring that has moved. Also check for dirt and build up on the tone rings.

 

[Joe Dirt]

Same issue on my '95, it was a dirty tone ring on one, dirty/ruined sensor the second time. Cleaned up and all was well.

I would just fix it correctly if I were you.

 

[nrschaaf]

Great info guys, looks like I'll have to dig into it when the blizards gone. Dirty is a definate with every part up here, they lay down enough gravel and dirt on the roads in the winter to fill a skyscraper. Does anyone know the spec for testing these sensors? My manual doesnt cover that and I'm not looking forward to buying a Ford manual if I can avoid it.