Hello, all. This is an update of a blog I wrote this past February on a recurring ABS code in a customer Workhorse chassis.
If you look back you will see that this vehicle has been a problem child and that at last post it looked like it had been fixed. Well, it came back again with the same issue! I don't know how long it was driven before the light set (I don't get to talk to the driver), but this is what we have been dealing with. We will fix a code issue, the repair will survive a test drive, then it will be back with the same code set.
I had addressed the issue last by switching two wires in the rear harness. These conductors run from one of the rear wheelspeed sensors to the controller at the front of the truck. It always bothered me that this fix solved the problem. The speed sensors generate an AC current which varies in frequency with the RPM of the wheel. I didn't think it would matter which way they are hooked up, since AC current is bi-directional, but when switching the wires seemed to solve the problem, I assumed it had to do with the controller's internal circuit path.
Anyway, it survived more than one test drive, so I didn't worry about it. After years of repairs, some of these questions of "why" not longer keep you up at night. If it works, it works. Anyway, the vehicle came back a couple of weeks later, same problem, same code. On one of the vehicle's previous visits one of the other guys ran a new twisted pair of wires from the other rear sensor to the controller bypassing the midships plug, and that took care of the intermittent code for that wheel, so I did the same for the other wheel this time. It looks like either the midship connector pins are causing an open, or the harness was handled roughly during factory installation. Since the problem came and went and the plug in question was often manipulated during our diagnosis, it would get my vote.
Anyway, the truck was in for a PM about a month after this last fix and the ABS light was out, so is looks like we finally have it nailed.
If anybody else has run into this problem and has any feedback, leave a comment or send an Email and I will post it.
Thanks.
If you look back you will see that this vehicle has been a problem child and that at last post it looked like it had been fixed. Well, it came back again with the same issue! I don't know how long it was driven before the light set (I don't get to talk to the driver), but this is what we have been dealing with. We will fix a code issue, the repair will survive a test drive, then it will be back with the same code set.
I had addressed the issue last by switching two wires in the rear harness. These conductors run from one of the rear wheelspeed sensors to the controller at the front of the truck. It always bothered me that this fix solved the problem. The speed sensors generate an AC current which varies in frequency with the RPM of the wheel. I didn't think it would matter which way they are hooked up, since AC current is bi-directional, but when switching the wires seemed to solve the problem, I assumed it had to do with the controller's internal circuit path.
Anyway, it survived more than one test drive, so I didn't worry about it. After years of repairs, some of these questions of "why" not longer keep you up at night. If it works, it works. Anyway, the vehicle came back a couple of weeks later, same problem, same code. On one of the vehicle's previous visits one of the other guys ran a new twisted pair of wires from the other rear sensor to the controller bypassing the midships plug, and that took care of the intermittent code for that wheel, so I did the same for the other wheel this time. It looks like either the midship connector pins are causing an open, or the harness was handled roughly during factory installation. Since the problem came and went and the plug in question was often manipulated during our diagnosis, it would get my vote.
Anyway, the truck was in for a PM about a month after this last fix and the ABS light was out, so is looks like we finally have it nailed.
If anybody else has run into this problem and has any feedback, leave a comment or send an Email and I will post it.
Thanks.
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