Hey all,

My ABS is kicking on intermittently when I am braking on dry pavement. It's usually when I'm going slower (less than 30mph), and is completely random. Maybe happens once or twice a day.

My ABS light usually stays off, although every now and then if the ABS engages "harder" than in the past, the ABS light will come on and stay on.

Any ideas? Should I clean all the sensors? I hear the rear diff sensor may be a common problem, but I'm not the type to start throwing parts at it to try and fix it.

Is there an easy way to isolate down which sensor may be giving it trouble? Or narrow it down to another component of the truck?

 

I've seen this issue on GM trucks. It's usually caused by a wheel speed sensor that is corroded or failing. On those, removing and cleaning the sensors often fixes the issue. Haven't seen this personally on a Ford, but I'd start by inspecting the sensors and tone rings for damage or corrosion.

 

I'd use a scanner capable of reading airbag codes to see what it might be.

 

I've had the ABS buzz intermittently for about 7-8 months or so. It always seems to come on in the morning and within the first mile of driving. It lights up the ABS light, but it will disappear upon a restart, even if it's just after the light came on. I ordered the new sensor and installed it last night when I was changing out the rear end fluid, light hasn't shown up yet, nor the ABS buzzing, but it is an intermittent problem so I can't diagnose it as cured. I just took a chance that the $50 sensor in the rear was the culprit.

 

So, I scanned it, and got code C1230 (Rear wheel sensor). I changed the sensor out, everything seemed good for a few days or so, and now it's back to doing it again. Not sure what else to change as there isn't much else back there.

 

Did you ever get any resolution for this? I have a friend with the same issue and we have already changed the rear ABS sensor. For troubleshooting purposes I wanted to tell you that the sensor should read a resistance of between 3.8 and 5.2 mega-ohms and the wires at the plug (with the key on) should read 9V. If the sensor doesn't read in that range it's bad and if the wires don't show that voltage there is probably either a break or a short. Other than those things it might be the ring in the diff. I haven't tested these things on my friends truck, but it's good info if you want it.

That being said, if you did get it resolved I'd like to know what the resolution was please!

 

Check the wiring connector to the rear sensor for corrosion , fairly common.

-Steve

 

I did not get it resolved. I am in the same boat you are. I put a new sensor in, and it still does it. I didn't know how to check the voltage, so I will measure the voltage on the wire and ohms on the sensor tomorrow and report back. Thanks for posting that info.

I'm wondering if my problem is in the ring, but I'm not sure how to check that. I assume the rear diff needs to be opened up for that.

 

I would assume that too, but it's possible that you could read resistance on the sensor and see if it changes when the wheels turn. If it does, you could mark a spot on the wheel, rotate it and see if there is any place where there is variance in the resistance pattern. If the resistance changes when the wheels are spinning and you see a spot that's different then you could feel a little more confident about opening up the diff.

Again, I'm just guessing, but it's worth a try.

 

Having same issue w/ABS light coming on. Can't go 1/4 w/o the light coming & staying on. Staring to drive me a bit crazy. Where exactly is the sensor located?
And by changing myself difficult? Thank for any input.

 

Sensor is in the top of the rear diff housing.

 

I replaced mine when I serviced the rear diff. I still have the same problem I did before where the ABS-inactive light comes on either at start-up or after the truck begins moving. It primarily comes on in cold weather, and will disappear and not return again if I turn off the ignition and re-start the truck. I didn't notice anything abnormal in the differential that would be setting off the sensor, so I'm chalking it up to a connector/wiring issue.