What causes ABS, ESP/BAS and SERV 4WD lights to light

KKboy · **Joined:** Tue Mar 04, 2008 10:36 pm **Posts:** 26

A week ago I had all these come on at once. The transfer case switch would not function to change from 2WD to 4WD. I took it to my dealer, who diagnosed a broken wheel sensor connector. Now repaired, all warning lights are gone. I did find one interesting phenomenon. Assuming the Liberty was in 2wd, if I set the transfer case switch to 4wd BEFORE starting the engine, the 4WD "engaged" display would show, and 4WD traction would operate. If I shut off the engine and reset the switch to 2WD, then started it again, the 4WD display would extinguish, and 2WD traction would operate. I mention this in case someone else suffers a switch failure-it seems you can still operate the transfer case this way. Who-da-thunk-it?

2008 Jeep Liberty North Edition 3.7

ajohns1288 · **Posted:** Fri Jan 03, 2014 9:28 pm

I had a similar issue caused by a bad wheel speed sensor. $15 and 15min under the back and it hasn't happened again.

What happens is the ABS computer sees the sensor acting up, so it knows it can't trust the readings, so it shuts down, which lights up the ABS, ESP/BAS, and Trac lights. The ABS module is constantly communicating with the Final Drive Control Module (FDCM), so when the ABS module stops talking, the FDCM freaks out too, which sets the Serv 4WD light.

TrueTexUSN · **Joined:** Thu Jun 13, 2013 11:15 pm **Posts:** 104

Does anybody have a part number or write up for correcting this issue?

ajohns1288 · **Posted:** Wed Aug 12, 2015 8:48 am

Front: 68004019AC
Rear: 52125003AB

These are for a 2008. The rears are pretty easy, just disconnect the wiring and unbolt the sensor using a 10mm. Takes all of 5 min and you don't even need to lift it.

The fronts are a bit more involved. You need to remove the front rotor to get access, but from there it's just as easy.

If you can find a code reader that can read abs codes, you'll know which one is bad.

TrueTexUSN · **Joined:** Thu Jun 13, 2013 11:15 pm **Posts:** 104

ajohns1288 wrote:

Front: 68004019AC
Rear: 52125003AB

These are for a 2008. The rears are pretty easy, just disconnect the wiring and unbolt the sensor using a 10mm. Takes all of 5 min and you don't even need to lift it.

The fronts are a bit more involved. You need to remove the front rotor to get access, but from there it's just as easy.

If you can find a code reader that can read abs codes, you'll know which one is bad.

The code I'm getting from my Hypertexh programmer is C102B, which from everywhere I've read is the right rear ABS sensor. My symptoms are exactly like the OP's. Thanks!

mattyvac · **Joined:** Mon Aug 26, 2013 1:22 pm **Posts:** 20

Wheel speed sensors, very easy fix and cheap part. Mine did it once too.

TrueTexUSN · **Joined:** Thu Jun 13, 2013 11:15 pm **Posts:** 104

Super easy, literally done in 5 minutes. Dealer wanted $160! I don't think so, Tim.

SheepDog · **Posted:** Sun Nov 29, 2015 2:05 pm

sounds like a fairly common problem. mine is doing the same thing.... what code readers read abs?? My Bully Dog GT did a dignostic read and nothing came up... any place that rents one out that can or is that strictly a dealer thing?

waysidecharlie · **Joined:** Sun Nov 16, 2014 11:12 am **Posts:** 46

I've had that combination come up. Shutting the engine off and restarting cleared it. Once I had to do that twice. It never happened after that.

Chereveco9 · **Joined:** Wed Jun 21, 2017 4:53 pm **Posts:** 22

In my case was s broken connector to the rear right ABS sensor... Mopar sells the part...

Good luck!!!!

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What causes ABS, ESP/BAS and SERV 4WD lights to light

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