My '06 CRD suddenly has the ABS, ESP, and the anti-skid icon lit up always. I read the DTCs, and U0121 "lost communication with anti-lock brake module." is active. I've cleared it, but it comes right back.

It just happened the other day as I was driving. The ESP and anti-skid lights came on (was just driving straight, no bumps), but just as I was about to enter a turn that had a speed bump. So 2 seconds after those lit up, I enter the turn that also has a speed bump, and the ABS light came on. (It was one of those giant plateau type of speed bumps, so I didn't hit it hard or anything, no change rattled, etc, etc.) I'm not convinced the ABS and speed bump were related.

The snow is melted right now, so I don't have any immediate place to test the brakes under ABS conditions without doing 45 into a sudden stop.

The rear wheel speed sensor connectors are attached and not rotted, all fuses are ok. ODO is working correctly, too. So I don't think it's related to the issues with the rear speed sensors I've read about.

I disconnected the battery for an hour, but the warning lights came back immediately when I started it back up the first time.

Is there anything else that is obvious? I went through the service manual that's available on this site (which you have to search for "U0121" in the pdf, as it doesn't show up in the bookmarks list!). There's no real helpful debugging info available. I see the wiring diagram, but before I start riping about wiring harnesses and such, has anyone had a similar issue? was it solved? Any other suggestions?

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06 Liberty CRD Sport
Virgin to mods so far.

Post this in the "Liberty CRD...Love that Torque!!!" forum.
This tech section is for telling us what you know (information, how to, procedures, etc).


Also, I believe, gassers have the same ABS/ESP module as the CRD.

Thanks, I dropped this in the overall Liberty category. An admin can remove this post if the double post thing is annoying.

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06 Liberty CRD Sport
Virgin to mods so far.