Diff Lock and ABS light coming on after driving 45 minutes (1 Viewer)

[1loverasta]

This is a weird one - I have a 93 with only a center locker. After driving about 45 minutes, the ABS and diff lock light start to flicker and then come on. If I pull over, shift into 4L and then back to 4H, the Diff lock light usually goes off but the ABS light stays on. I don't think the locker is actually locked, but I do think the ABS is genuinely disabled. My mechanic has been troubleshooting it for months and he's ready to give up. He'll mess with it and then I'll go pick it up, drive it for an hour and bring it back. This has been happening every few weeks since the Summer.

I read in another thread that a guy had a somewhat similar experience where he had an exhaust leak that was pointed at a wiring harness and melted it. I don't think that's the case here since I would have completely melted anything a long time ago.

I've read in other posts about Diff Lock & ABS light coming on or staying on, but this seems to be unique in that it only happens after driving about 45 minutes. It's almost exact too - it happens on the same stretch of road about 30 miles from my house.

Any ideas?

 

[ERG80]

What has your mechanic checked?

Have you or your mechanic checked the transfer case cdl lock sensor?

 

[1loverasta]

What has your mechanic checked?

Have you or your mechanic checked the transfer case cdl lock sensor?

Yes, he replaced it. This has almost become comical - he doesn't want to rack up a ton of hours on this, and he happens to have a new, young tech who also has a 93. So any time the new tech doesn't have any work, he's having him check every wire and connection from the CDL to the battery - so far nothing.

 

[Malleus]

Stay off that road

 

[Malleus]

Sorry, that was too easy.

Seriously, have you checked the operation of the control relay (ppg 136-137 of the EWD?

 

[Malleus]

It's probably best, when trying to solve a problem that isn't a known fault with a known solution, to actually go through the steps, one by one. Relying on old posts here may not be the best way to solve this problem.

I'd start with ppg IN-10 to IN-12 of the FSM (it's in the Resources section, along with the EWD if you don't have a copy); just for the sake of completeness.
Then I'd go to the Transfer Section, TR-51:

 

[Malleus]

This is a standalone system, so it's not too hard to go through the whole circuit. If the problem isn't electrical, you may have a problem with the sensor seeing its target. Hard to visualize, but that's all that comes to mind.

HTH

 

[ppc]

Yes, he replaced it. This has almost become comical - he doesn't want to rack up a ton of hours on this, and he happens to have a new, young tech who also has a 93. So any time the new tech doesn't have any work, he's having him check every wire and connection from the CDL to the battery - so far nothing.

There are three sensor/switches on the transfer case. Exactly which one was replaced?

Keep in mind that once ABS gets disabled and vehicle speed exceeds ~33mph the ABS system will stay disabled until the vehicle is shut off no matter the state of the CDL.

 

[1loverasta]

There are three sensor/switches on the transfer case. Exactly which one was replaced?

Keep in mind that once ABS gets disabled and vehicle speed exceeds ~33mph the ABS system will stay disabled until the vehicle is shut off no matter the state of the CDL.

Ok good to know. How long does it need to be shut off? Because I've pulled over and shifted in and out of 4L and it seems to turn the CDL light off (mostly not always). But if I turn off and restart, the ABS light usually stays on, unless I turn off the car for an extended period - like a few hours or overnight.

 

[ppc]

Ok good to know. How long does it need to be shut off? Because I've pulled over and shifted in and out of 4L and it seems to turn the CDL light off (mostly not always). But if I turn off and restart, the ABS light usually stays on, unless I turn off the car for an extended period - like a few hours or overnight.

The time it takes to reset is not documented but should more or less be instantaneous. Are you pulling the key from the ignition before restarting.

First thing to do is disconnect the CDL sensor connector on the front of the transfer case. Neither CDL or ABS light should be illuminated. If not then its time to test all the wiring looking for a short circuit to ground.

Report back before any changes are made.

 

[jonheld]

Ok good to know. How long does it need to be shut off? Because I've pulled over and shifted in and out of 4L and it seems to turn the CDL light off (mostly not always). But if I turn off and restart, the ABS light usually stays on, unless I turn off the car for an extended period - like a few hours or overnight.

As soon as you shut down the engine, the ABS is reset.
Below is a picture looking at the top of the transfer case. The CDL switch is towards the front of the transfer case.
The CDL switch triggers both the CDL dash lamp and ABS. As previously mentioned, I would disconnect that as a first step.