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Ford Ranger ABS acting strange

I have a problem with the ABS system on my 2001 Ford Ranger. The ABS system intermittently activates when stopping on dry pavement. To diagnose the problem, my mechanic attached a Snap-On scan tool and drove the truck. The front wheel speed sensors and the rear axle sensor all indicate approximately the same speed. However, occasionally, when the speed gets below 4 mph, the ABS activates and the scan tool screen is totally blanked out. It’s as if some type of pulse is being sent back through the OBD II that zaps the scan tool. No code is recorded and the ABS dash light does NOT come on. My mechanic is at a loss, since he can not capture a code to diagnose the problem. He is suspecting some type of voltage spike but doesn’t know where or how to find it. He has checked the reluctor ring and can’t find anything wrong with it. Someone suggested to me that the front wheel bearings could be loose or bad causing the air gap to widen under certain turn or suspension travel conditions. I checked the shop manual and can’t find any reference to wheel bearings on a Ranger 4X4. What am I missing? Is the wheel bearing a likely cause? What else could be the cause?

If it’s a 4WD and it is in 2WD, a rear tire may be trying to lock, especially if you have no weight in the back and if there is a little dirt on the road. It may be normal. Try puttting some weight in the back or stopping a little easier. See if the tire pressure is right and not overinflated. Maybe a little experimenting will stop the problem. If one rear or front tire is low or a different size it could cause a problem.

I did some further testing and it happens in either 2wd or 4wd. Tires are all the same with even tread wear and inflation. The ABS engages even on a clean dry road. The strange thing is the light on the dash doesn’t come on to indicate any kind of fault. Also can’t get a scan tool reading once the ABS engages.

Bet you its the front left sensor in the hub assembly.

Your problem sounds like one i encountered.

Sounds to me like a bad ABS computer.

I agree, it sounds like a voltage spike. I would suspect the charging system as the problem. BUT!! it could be very hard to pinpoint.

You could have the charging system checked and it may not show any voltage spike when it is being checked.

I would also check the battery ground cable, make sure the connections are tight on the battery and the engine block.

As mentioned it could be a module problem. One way to check it would be to disconnect a wheel speed sensor and drive the vehicle. Se if it sets a code for the disconnected sensor. If there is no code I would suspect the module.

Voltage spike my foot! Why would there be some random “voltage spike” every time the speed got down to a low number. This has bad computer written all over it, or possibly bad scan tool.

I’d try to swap in a junkyard ABS computer to see if that helps.

Just goes to show how little you know about cars.

Just because you haven’t seen it doesn’t mean it can’t happen. I have seen it happen.

Switching out parts to see if there is a problem is a pretty stupid suggestion as well. I gave him a perfectly good way to check if the ABS module is working and it doesn’t cost a dime to do it my way.

Shotgunning parts at a problem is never a good way to diagnose a problem.

I have seen voltage spikes. I have repaired enough electronic stuff damaged by them to know what it causes. The symptoms stated don’t add up to a “voltage spike.”

The test you suggest may identify a bad computer, but also may not. The problem always occurs at low speed and blanks out the scanner. The only thing that should affect the scanner is the computer, or the scanner itself. I am not suggesting a shotgun parts replacement. I have specific reasons, based on the stated symptoms, to try swapping the ABS computer.

That’s all I’m going to say on this thread. I do hope the OP comes back if/when it gets fixed and tells us all what the problem turned out to be.

I’m having the exact same issue with my 01 ranger 2wd How did you resolve the issue

It was 11 years ago and he’s never been back after posting his question, so we assume his truck, if still running still has the same problem.