1999 Dodge Durango ABS control module

Hi GroovyGal64. Welcome to the forum. I don't want to second-guess your diagnostics, especially since I can't be right there to observe the symptoms, but my gut feeling is this is not a controller problem unless the brakes are locking up when you say they are "grabbing". If you mean they are pulsing when you apply the brakes, they are doing what they are supposed to do, the problem is WHEN they are doing it.

Different size tires will cause this problem. Another common cause that is often overlooked at first is a cracked tone ring on one of the front wheels, but that will also cause the yellow warning light to turn on and the system to turn off.

There are always two fuses for the ABS controller. If one blows, the other circuit provides the current for the warning light. Unplug either one of those fuses to disable the system. That will leave you with the regular base, or "foundation" brake system just like any other truck. If you still have a brake lockup problem, it is not related to the anti-lock system. A common cause of rear wheels locking under light pedal pressure is a rear parking brake cable stuck partially applied.

Caradiodoc

"Thanks for your prompt reply. Just for clarification... The "grabbing" isn't occurring during any kind of braking... It's occurring while driving. It's intermittent and can be mild to severe... Or not at all! Worse with warmer weather, and typically worse with more engine strain (but... Not always). Can occur at highway speeds or just running around town. Like the ABS/brake light issue (where the lights would come on only after a certain drive time, temp or going over a bump), it would typically take 5-10 minutes before it would start doing it, but now it's just getting worse. So it's a mystery, seems like an electrical issue and that's what the folks at my repair shop (who've gone over this vehicle on about 5 other occasions) believe, that the ABS controller is sending faulty messages to the brakes and trying to stop the car, and not during any braking. Very weird. The ABS and brake lights have been on for some time, but braking has never been an issue, even now. Have had to hard brake on a number of occasions and they've been good. Replaced the front brakes in February, they were a little worn. Did replace the rear wheel speed sensor, too, just to see if that would resolve, but it didn't. Wasn't having a speedometer issue.

Other concern was it might be the tranny going; it's got lots of miles and does have some issues (doesn't like to get out of the lower gears that easy). But... Guys at the shop are not pinning it on anything mechanical at this point! Recently had spark plugs replaced; the #5 plug had some crazy buildup on it, the others were clean. That didn't fix the issue. Will be getting to the other regular tune-up stuff in the next week or so (rotor, distributor cap, PC valve, etc.).

Any ideas you may have would be appreciated! Don't want to put much into the ol' beast, it's been a decent vehicle and great for hauling, but I'm looking for something newer and more gas-friendly in about 6-8 months. Just need it to last that long at least!

Thanks for your help!"

GroovyGal64

First of all, the ABS should not do anything until voltage is received from the brake light switch, so yes, I suppose the computer could be erroneously activating a solenoid in the hydraulic controller which sends pressurized brake fluid to a wheel. A valve could be leaking too in the hydraulic controller. If you pull the fuses and the problem goes away, that will be a clue. A leaking valve could cause a brake to grab but it will not pulsate like they normally do when the ABS kicks in. A shorted driver transistor in the computer will also apply a solenoid without pulsing it. If you hear or feel the brake pulsate when it grabs, the computer and the hydraulic controller are doing what they're supposed to do but in response to a wrong input. That COULD also be caused by a problem in the part of the computer that reads the wheel speeds and brake switch input.

Regardless, this is not a common problem which can make it hard to diagnose. If the same problem occurs after the ABS fuses are removed, you have a regular brake problem. I have a lot of things to look at then.

Caradiodoc

Well, this is one for the memory banks. I can only surmise that some arcing was taking place between the contacts in the distributor and it was radiating a signal magnetically to the ABS wiring. I remember hearing about some Ford trucks that would continue to pulse the brakes after it had come to a complete stop. They traced those to spark plug wires that were laying too close to other wiring harnesses and inducing voltage spikes into the ABS sensor wiring.

You should still have the codes read in the ABS computer. Some will not erase codes automatically. Once they are erased with a scanner, the warning light will go out and the system should work properly again.

Thank you for sharing the fix.

Caradiodoc