"4WD SERV" warning light override

[LeeLand]

I recently had a lift kit installed on my 2018 JLUR. During the install process the front passenger ABS (wheel speed) sensor was stretched and damaged. This caused the following warning lights to come on: ABS, Trac Control, 4wd Serv. In researching this problem the simple solution is to replace the wheel speed sensor (Mopar Part #68394210AD). What I discovered is that that part is in scarce supply. The estimated delivery time from Mopar was 14 days and you can't find an after market equivalent anywhere. Although the JK sensor looks identical, it is not and does not work.

So the issue is this, while waiting for the part I have no ABS, Traction Control, and the big one...no 4WD! The wheel speed sensor error triggers a message that says "4wd temporarily unavailable" and lights up the warning light "4wd Serv". If you shift the Jeep into 4H it will not engage and the 4H does NOT light up on the center cluster. If you shift into 4L the gearing in the rear end changes but the TC does not lock and there is no power to the front diff. The front sway bar disconnect, and front and rear locker feature were also disabled. This was upsetting to me, because I desperately wanted to take the jeep out and test out the new lift kit, and didn't want to wait the 14 days for the part to arrive.

The Solution:

I was finally able to shift the jeep into 4H and 4L and use all of the Off Road Features.

In order to override the "4WD SERV" warning I did the following.

1. Put the Jeep in Park and turn the Jeep OFF
2. Shift the 4WD Lever to the 4H position
3. Start the Jeep
4. The Transfer Case should lock and engage the 4H before the computer has a chance to do a system check and discover the error codes. If it is successful the 4H will be lit on the center cluster. (the 4wd Serv light will stay on)
5. All 4H, 4L and all 4WD features will now be available and work normally as long as the Jeep is left running.
6. the ABS and Traction Control will still NOT WORK.

This hack may come in handy if you have a bad sensor on the trail and need 4WD to get home. Please let me know if you have any experience with this issue or any other suggestions. Thanks.

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[TCogs1]

Thank you for the write up...This weekend I was running trails with Point Magu 4x4 club and after the second or third trail, I noticed the sway bar was disconnected and I could not engage the lockers.. Needless to say, I was about to need them (obstacles ahead)..

Because this software based logic freaked me out as I did not know how to defeat it or what would happen next, I decided to return to base camp and learn more. Once at base, I shifted out of low range, no impact, then shut the Jeep down, waited a couple minutes, then fired it back up and everything was resolved... Went for smoke run to see if it would repeat, so far so good.. Today I am on this forum learning more, next week I will take it to the dealer see what they say..

Needless to say, software should never stop the ability to engage $x and lockers..

All tips welcomed!

Again thanks for the post!!

 

[Az-jewel]

I’m currently waiting for a wheel speed sensor too. why is the manufacturer unable to make this part? It’s been a year since the original post and still weeks to get the part?

my shop, that trussed my axle (the cable got pinched between the spring and axle truss because they didn’t reconnect the clip that keeps the cable tucked out of the way-and the dealership wouldn’t help since my Jeep was modified) soldered it for me so I could enjoy a weekend wheeling trip,
even though the abs and esc lights went out the SERV 4WD light cane on shortly after being in 4WD . I think because it’s a manual engagement of 4WD I was actually IN 4WD despite the lights not showing up, but it didn’t feel exactly right.
in any event, I’m still wishing and waiting for the part to arrive. It’s been 2-3 weeks now! super frustrating!

 

[jludave]

It’s been 2-3 weeks now! super frustrating!

Wow, that's just crazy. I had a wheel speed sensor go on my '15 JKU last year. I was in and out of the dealer for the repair in about 2 hours. I wonder what the deal is with the sensor for the JL? It can't be that much different than the one for the JK. Hope you get yours soon. Good luck!

 

[scrape]

Thank you for the write up...This weekend I was running trails with Point Magu 4x4 club and after the second or third trail, I noticed the sway bar was disconnected and I could not engage the lockers.. Needless to say, I was about to need them (obstacles ahead)..

Because this software based logic freaked me out as I did not know how to defeat it or what would happen next, I decided to return to base camp and learn more. Once at base, I shifted out of low range, no impact, then shut the Jeep down, waited a couple minutes, then fired it back up and everything was resolved... Went for smoke run to see if it would repeat, so far so good.. Today I am on this forum learning more, next week I will take it to the dealer see what they say..

Needless to say, software should never stop the ability to engage $x and lockers..

All tips welcomed!

Again thanks for the post!!

Wire your lockers to your factory aux switches if you have them, or aftermarket switches, using part#77072413

That will prevent any software logic from preventing you from using your lockers.

Then as far as 4wd. It is not the transfer case preventing engagement as the op suggested. It is the FAD. If you delete the FAD, there is no other electronic/computer controlled system that will lock you out of 4wd. It’s entirely mechanical except for the FAD.

Now for the front sway bar, Evo mfg makes a manual or air actuated sway bar disconnect for the rubi sway bar motor. Or you can just delete your front sway bar entirely, or switch to a Sport sway bar with quick disconnect links. Or any combination of the above.

All that stuff should prevent your Jeep from getting stranded just because some computer code is preventing you from using all your toys.

 

[Geronimo]

Wire your lockers to your factory aux switches if you have them, or aftermarket switches, using part#77072413

Are you saying do away completely with the factory locker switch and run power on/off from the AUX switch? would this also mean you could conceivably engage lockers at any speed you were traveling?

 

[word302]

So so we're clear, they're is no software keeping anyone's transfer case from engaging. It is completely mechanical. The issue keeping you from getting power to the front wheels is the FAD, which is why the op could engage low range but to the rear wheels only. The transfer case lever is a direct mechanical connection to the transfer case.

 

[scrape]

Are you saying do away completely with the factory locker switch and run power on/off from the AUX switch? would this also mean you could conceivably engage lockers at any speed you were traveling?

yes, yes, and yes.

 

[Roky]

Are you saying do away completely with the factory locker switch and run power on/off from the AUX switch? would this also mean you could conceivably engage lockers at any speed you were traveling?

I’ve been running my lockers on aux switches 3 and 4 for almost 2 years now, no issues.

 

[Geronimo]

I’ve been running my lockers on aux switches 3 and 4 for almost 2 years now, no issues.

That sir is one of the most valuable bits of information I have seen anywhere. Simple straight forward and a killer solution to many issues. This must be done along with FAD delete. Reliability is the word of the day

I appreciate that greatly Mr. Roky !

 

[Geronimo]

I’ve been running my lockers on aux switches 3 and 4 for almost 2 years now, no issues.

By which method did you FAD delete? If you don't mind saying

 

[Roky]

By which method did you FAD delete? If you don't mind saying

I’m still using the fad....... But the best way in my opinion, is to replace the 2 piece axle with a one piece axle like the rcv........

You can see the indentation on the axle shaft in the picture, that’s where the fork of the fad is located. So when you engage to 4wd the fork still moves so it doesn’t throw any nanny codes. It still thinks it’s working.

 

[Roky]

That sir is one of the most valuable bits of information I have seen anywhere. Simple straight forward and a killer solution to many issues. This must be done along with FAD delete. Reliability is the word of the day

I appreciate that greatly Mr. Roky !

No problem

 

[limeade]

By which method did you FAD delete? If you don't mind saying

I just did the FAD delete with the Dana Chromoly shafts. You completely remove the FAD module and put a plate over the FAD housing opening. A Tazer mini then can turn the FAD off, otherwise it won't go into 4WD.

I definitely like the idea of wiring the lockers to my Aux switches........thanks for the info @Roky

 

[limeade]

I’ve been running my lockers on aux switches 3 and 4 for almost 2 years now, no issues.

Did you simply re-route the factory wiring or did you buy two new wiring harnesses so the stock switches could be reactivated if necessary?

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