ESP/BAS Warning Light

About 5 miles after I hit the highway back to Moab after our last (hard) run, the ESP/BAS warning light came on along with the traction control light. I couldn't feel anything different on the drive back into town, but after doing some tight turns at low speed (4-hi) it seemed like the ELSD were locked. I ended up disconnecting the ELSD connectors from the front and rear diffs (and got the CHECK 4WD SYSTEM error of course) and drove down the highway again for a mile or so and the ESP/BAS warning went off. It came back on the next day and stayed on for the 380-mile drive back from Moab. It seems like the ELSD has quit working altogether (I can't hear the whirring noise when the diffs lock when I go into 4LO the way I could before and the ratchet sound in hard turns is gone). Are they totally electronic (i.e. solenoids), or do they also use air/vacuum? I checked most of the fuses but a lot of them are only identified by acronyms (none of which was ELSD) and all look good. Can one of you mechanics point me in the right direction?

There completely electronic. Check all the basics first fuses connections and stuff then try to reset the computer. you could try that thing crunchy just dis to I guess. Did you do the key dance any codes being thrown. These systems seem to be very touchy :(

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Originally Posted by Sal-XK

There completely electronic. Check all the basics first fuses connections and stuff then try to reset the computer. you could try that thing crunchy just dis to I guess. Did you do the key dance any codes being thrown. These systems seem to be very touchy :(

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I checked all of the under-the-hood-fuses but haven't checked the under-the-dash fuses yet. I did try the lock-to-lock voodoo dance several times that worked for Crunchy, but no luck. How do I reset the computer? ...disconnect the battery? And, what is the "key dance"?

The ELSD's are actually a gyropump within the diff that creates hydraulic pressure when there's differing wheel speeds. The electronic version of the diffs is actually a solenoid valve which moderates how much of the pressure is applied to the clutches... full open on the valve results in a "locked" diff.

Remind me tomorrow evening and i'll pull out my service manuals to see if you can run a test using a DVOM to see if the solenoid in the diff is stuck or not (usually you can do this by checking the resistance).

When was the last time you changed the diff fluids? I'm sure MOAB trail riding with some 33" tires put those axles to work... HARD... may be worthwile getting some fresh fluid in there with some friction modifier. As the fluid starts breaking down you'll get more "chatter" than normal from the clutches.

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Originally Posted by Matt_

The ELSD's are actually a gyropump within the diff that creates hydraulic pressure when there's differing wheel speeds. The electronic version of the diffs is actually a solenoid valve which moderates how much of the pressure is applied to the clutches... full open on the valve results in a "locked" diff.

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So what is the "whirring sound I hear when I shift in/out of 4LO? Is that the transfer case? I assumed it was the diffs since I can still go into 4LO but no longer hear the sound.

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Originally Posted by Matt_

Remind me tomorrow evening and i'll pull out my service manuals to see if you can run a test using a DVOM to see if the solenoid in the diff is stuck or not (usually you can do this by checking the resistance).

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I have a DVOM and will remind you tomorrow.

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Originally Posted by Matt_

When was the last time you changed the diff fluids? I'm sure MOAB trail riding with some 33" tires put those axles to work... HARD... may be worthwile getting some fresh fluid in there with some friction modifier. As the fluid starts breaking down you'll get more "chatter" than normal from the clutches.

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I had it changed not that long ago--January, I think.

That's the t-case shift motor making that sound.

Ok so here's the scoop...

Check the resistance of the solenoids. If the resistance is above 50 ohms:
Inspect the front differential solenoid jumper harness connector, repair/replace as necessary. If OK, replace the shorted front differential solenoid in accordance with the service information. (same for the rear)

If solenoid isn't shorted, there's a whole bunch of tests to do on the control side of the harness... but a lot of them require activating the circuit with a scan tool and checking for output with a test light. There's also instructions for checking for shorts... but it depends whether the DTC is for a high or low voltage circuit fault; and typing up all 40 pages is, well, a lot of work! So see what resistance you're getting and go from there.

If you have a way of pulling the code that would help a lot with the troubleshooting.

Thanks for looking that up. I'll check the solenoids first then see if my brother's reader is compatible with Jeeps.