ABS speed sensor problem

[verhague]

The ABS light on my 2000 F250 is driving me crazy.
I have replaced the speed sensor on the rear axle twice and still have the problem. The ABS light will either flash or stay constantly on with the speedometer bouncing all over (when flashing) or not working at all (when on). The OD light will also flash when the ABS light is constantly on. I have even checked the connector at the sensor with an ohm meter to see if there is a problem with the plug, it checks good. The only thing that makes me not question the sensor again is that it will work at times. I had made a 90 mile trip two days ago and it worked fine. The next day I drove on a very rough/bumpy road and the darn thing came back on. Driving on the same road may make it go off again, but it has not yet. It's as if a something comes loose elsewhere in the circuit/wire.
Any thoughts?

[mschn99]

id start to wonder about possibly something in the rear differential being out of wack....maybe loose bearings or something causing the tone ring for the sensor to be off....

If i was you, i would do a differential service and drain the fluid into a clean pan. Inspect the fluid for any signs of metal contamination. Also, then spin the differential (have the truck on jackstands and in nuetral) and see if the tone ring is obviously distorted at all or if you can push the ringear side to side by hand at all....

[verhague]

I just serviced the rear end. I did not think to try moving the carrier side to side but I did look very carefully at the pickup (ring) for the sensor and it looked good. Looking and the bearings, axles and carrier for play/slop is an excellent idea. I wish I would have thought of that when I had it a part. Now I need to try and capture and reuse the gear oil. That 75/140 synthetic plus XL-3 is not cheap. Thanks for the suggestion. I'll try anything right now.

[straycat]

Let us know how it turns out.

Gord.

[verhague]

Well, I spent most of the day Sunday taking this thing a part again and found nothing wrong. The pickup ring for the ABS sensor looked like new and the differential had no play. The left wheel hub had a little play so I removed the axle and adjusted it. Everything is nice and tight.
The problem still occurs.
It will work sporadically with no lights being on and the speedo working good and then #$%@!
I had read somewhere here before that someone had to trace down the wiring and found a short. I don't remember more that that. I’ll try another sensor, this one from Ford, and give it a go.
I'll keep you updated on my progress, if I have some.

[WEWILLE]

scan it for codes, it may be a sensor up front.

[Rob]

what about having your ABS control module checked out, i had the same problem on my 99 Dodge dakota, and it turned out being the module. i went through several speed sensors. have it checked and go from there. Good luck!

[hfsess]

I have an 05 F-250 6.0 and am having similar problems. When the ABS light comes on the cruise control will kick out, lights will flash and the ABS light stays on for a considerable time, at least a couple of weeks then goes off for no reason.
I am still in warranty and will be taking mine to dealer soon. If I learn anything I will post.
Howard Sessions

[cblackb]

Hey All, sorry to start up an old thread again, but this is the exact problem I'm having (I think) and I need some help. First my ABS light came on, then it went off for awhile and it's been doing this for about a week. Last night I fueled up and started my truck and was driving and noticed that my speedometer was dead, stuck on zero and my OD light was blinking, but I had NO ABS light on. So I pulled over and cycled the key a few times and now it's working again with no lights on..for now. So what exactly is this sensor and where is it (rear diff?)? Any ideas about this? Thanks!

[verhague]

Sorry about the late update.

I believe I have fixed the problem but I'm still not sure what it was. Here's what I did.

With the batteries disconnected.

I removed/unplugged all the items on the driver's side inner fenderwell (battery, air box, etc.) and removed the inner fender. I unplugged and cleaned (with brake cleaner and compressed air) every plug I could find including the 3wire harness plugs (10mm) to the firewall and the plug to the PCM (long plug w/10mm). I removed the PCM (from inside the truck) and cleaned all the contacts on that as well.
I unplugged the ABS control module and cleaned the contacts on that using the brake cleaner and compressed air (the ABS control module, rear only, is located under the battery box behind the headlight). After cleaning all these items I put a little dielectric grease around the plugs (to prevent water from entering) and plugged everything back in. While I had the inner fender off I took a pressure washer to that side of the engine/frame and gave it a good washing too.

I put it all back together and hooked the batteries back up and no ABS light. Everything works, including the speedometer, and has been for the last few months. I have driven it on the bumpy roads (with my fingers crossed) and the light does not even flicker.

So far so good.