Service 4wd Light

Milesofsmiles · Mar 10, 2023

I first had my service 4WD light come on when I was driving home from the dealership. It felt like the front locker was engaged due to it binding when turning sharp. It would reset after turning the Jeep off then restarting. I noticed if I turned off traction control and held the traction control button to disable stability control it would turn off the front locker. There never was any indication on the dash lights or off-road pages on my radio to say the locker was ever engaged. It was though! Tested it. I pushed in all the fuses and checked every connector under the Jeep. Kept having the problem. I now have 6k miles on my Jeep and I have fought it since I bought it August 2022. A week ago I decided I was taking it in for service at the dealership. I had installed a Tazer mini about a month after bought it so I needed to uninstall it. While under the dash trying to remember how I initially installed it I noticed something strange. I found an ELO tracking device. After lots of investigation I found out the dealer had installed it and never told me. I paid cash for the Jeep so there was no reason for it being there. It was tied into the OBD2 port with a pigtail wiring harness and hidden behind the plastic kick panel. Now since it’s gone I have not had the service 4WD light come back on and the traction control button acts different too. I’m curious if that GPS tracker was causing issues since it taps into the can-bus system. I looked up the schematic and yes it does tap into the Can-bus. What do y’all think?
Todd

Jgc650i · Mar 10, 2023

dog said:
I just replied to your other thread where you were talking about the SERV 4WD light - now I'm terrified, sounds like we have exact same symptom - wheels feel like they're binding on tight turns...

I just noticed this today, and definitely haven't ever had this happen before... so I'm hoping it's not trashed. Obviously still under warranty, but *really* hoping to avoid new transfer case!

Dog, I’m curious, whatever happened with this for you? What turned out to be cause and solution?

HEAT392 · Mar 10, 2023

Milesofsmiles said:
I first had my service 4WD light come on when I was driving home from the dealership. It felt like the front locker was engaged due to it binding when turning sharp. It would reset after turning the Jeep off then restarting. I noticed if I turned off traction control and held the traction control button to disable stability control it would turn off the front locker. There never was any indication on the dash lights or off-road pages on my radio to say the locker was ever engaged. It was though! Tested it. I pushed in all the fuses and checked every connector under the Jeep. Kept having the problem. I now have 6k miles on my Jeep and I have fought it since I bought it August 2022. A week ago I decided I was taking it in for service at the dealership. I had installed a Tazer mini about a month after bought it so I needed to uninstall it. While under the dash trying to remember how I initially installed it I noticed something strange. I found an ELO tracking device. After lots of investigation I found out the dealer had installed it and never told me. I paid cash for the Jeep so there was no reason for it being there. It was tied into the OBD2 port with a pigtail wiring harness and hidden behind the plastic kick panel. Now since it’s gone I have not had the service 4WD light come back on and the traction control button acts different too. I’m curious if that GPS tracker was causing issues since it taps into the can-bus system. I looked up the schematic and yes it does tap into the Can-bus. What do y’all think?
Todd

Yes to the front locker activating with this light, at low speeds
Uhh … oookkkk … to the ELO tracker…
No to the tracker causing this

Check transfer case fluid and diff fluids

guruman · Mar 10, 2023

Our transfer cases have an electric clutch mechanism on the front output, in 4h auto (really all-wheel-drive) this clutch allows some slip to prevent driveline bind on high-traction surfaces. This same clutch is what is disengaged when "forcing" 2wd with the Tazer.

It's much more likely that this clutch is causing the "service 4wd" message. if it is stuck in the fully engaged position, the driveling will bind when turning on high traction surfaces. I think this is being mistaken for the front locker being engaged. The locker has a sensor that causes the locker indicators to come on, even if the locker is commanded to be "off", this is to let you know when the lockers do not disengage right away. So, unless you are getting a locker indicator, the locker is probably not engaged. Temporarily disconnecting the front axle locker connection would prove or disprove this theory.

I think it's more likely the clutch or whatever activation mechanism controls the front output that is causing these "service 4wd" issues. IF that clutch mechanism in canbus controlled, then something interfering with the canbus signaling might effect it, but. I would think we'd see issues elsewhere, and not JUST the 4wd output.

HEAT392 · Mar 10, 2023

guruman said:
Our transfer cases have an electric clutch mechanism on the front output, in 4h auto (really all-wheel-drive) this clutch allows some slip to prevent driveline bind on high-traction surfaces. This same clutch is what is disengaged when "forcing" 2wd with the Tazer.

It's much more likely that this clutch is causing the "service 4wd" message. if it is stuck in the fully engaged position, the driveling will bind when turning on high traction surfaces. I think this is being mistaken for the front locker being engaged. The locker has a sensor that causes the locker indicators to come on, even if the locker is commanded to be "off", this is to let you know when the lockers do not disengage right away. So, unless you are getting a locker indicator, the locker is probably not engaged. Temporarily disconnecting the front axle locker connection would prove or disprove this theory.

I think it's more likely the clutch or whatever activation mechanism controls the front output that is causing these "service 4wd" issues. IF that clutch mechanism in canbus controlled, then something interfering with the canbus signaling might effect it, but. I would think we'd see issues elsewhere, and not JUST the 4wd output.

Thanks Guru
The dash / UConnect / off road pages etc does not read locker connected but it drives like it (at low speeds with this light on)

….is everyone here using a Tazer ?

Milesofsmiles · Mar 10, 2023

HEAT392 said:
Yes to the front locker activating with this light, at low speeds
Uhh … oookkkk … to the ELO tracker…
No to the tracker causing this

Check transfer case fluid and diff fluids

I just checked the fluid level in the diffs and the transfer case. Levels were perfect in all. I’ll just have to wait it out to see if the light comes on again.

HEAT392 · Mar 10, 2023

Milesofsmiles said:
I just checked the fluid level in the diffs and the transfer case. Levels were perfect in all. I’ll just have to wait it out to see if the light comes on again.

Dang
Yeah I checked the same recently hoping for different results but had the same as yours here
I haven’t seen the light in awhile
A few things that were associated with it coming on for me:
Long continuous drives 800+mi
Long continuous drives in off-road+ <200
Long continuous drives <100 in off-road+ with TC ON seemed to pop it pretty quick and it’s been awhile since I ventured with those settings as I’m not excited to recreate it
Would pop on at rest stops/gas station after coming to a halt on these drives
Finally, I’m approaching 30k
Seen this first at <3k and intermittently throughout ; total of maybe 6 times
Last spotted maybe 25k
And honestly, I have more than once cleared it with the Tazer and kept moving

Milesofsmiles · Mar 10, 2023

HEAT392 said:
Thanks Guru
The dash / UConnect / off road pages etc does not read locker connected but it drives like it (at low speeds with this light on)

….is everyone here using a Tazer ?

I tested my front diff. With light on and binding I disconnected the front diff plug. The locker unlocked and I got a front diff warning light.
The tazer does cause issues on some things. Try pushing and holding your traction control button. With the tazer I get warnings to service antilock brake system and service electronic stability control system. My coworker tried it on his 2020 Rubicon and it gave him the same messages. When I uninstalled the tazer I don’t get those messages anymore.

HEAT392 · Mar 10, 2023

Milesofsmiles said:
I tested my front diff. With light on and binding I disconnected the front diff plug. The locker unlocked and I got a front diff warning light.
The tazer does cause issues on some things. Try pushing and holding your traction control button. With the tazer I get warnings to service antilock brake system and service electronic stability control system. My coworker tried it on his 2020 Rubicon and it gave him the same messages. When I uninstalled the tazer I don’t get those messages anymore.

Paging @justjoez
Any idea TazerBoss?

thexr6 · Mar 10, 2023

HEAT392 said:
Paging @justjoez
Any idea TazerBoss?

HEAT392 · Mar 11, 2023

Well I don’t know
It’s interesting a lot of us have seen this light
I didn’t connect it with Tazer but I wonder if 100% of us seeing it are running one.
I suppose it opens the door to one more thing to troubleshoot and eliminate.
I’m scratching my head with a few different mechanics trying to diagnose.

Latest Jeeper-only off-road shop master tech mechanic is telling me he’s seeing JL Jeeps - with and without the Tazer - getting false engagement on the axles - and they are locking up as a pattern right now
Could be a short in the electrical harness @ the differential?
Supposedly the shop had talked to Tazer folks recently about a new product they are coming out with ?
Resembles the issue, but isn’t the same. Shop has probably put through about 10 or 15 392 Jeeps at this point, for mods and/or maintenance

Edit: words

At Risk Ute · Mar 18, 2023

Thank you for all this information.

3800 miles and had just gone wheeling for the first time when I got the light.

I had pressed down my fuses when I picked up my Jeep. However, most of them were loose this time. Guess I’ll add this to my 5K maintenance checklist.

Robr651 · Mar 18, 2023

HEAT392 said:
Well I don’t know
It’s interesting a lot of us have seen this light
I didn’t connect it with Tazer but I wonder if 100% of us seeing it are running one.
I suppose it opens the door to one more thing to troubleshoot and eliminate.
I’m scratching my head with a few different mechanics trying to diagnose.

Latest Jeeper-only off-road shop master tech mechanic is telling me he’s seeing JL Jeeps - with and without the Tazer - getting false engagement on the axles - and they are locking up as a pattern right now
Could be a short in the electrical harness @ the differential?
Supposedly the shop had talked to Tazer folks recently about a new product they are coming out with ?
Resembles the issue, but isn’t the same. Shop has probably put through about 10 or 15 392 Jeeps at this point, for mods and/or maintenance

View attachment 18856

Edit: words

Electronic lockers are an issue on the JL’s and Tazer came out with these to fix the issue:

Z Locker OEM – Z Automotive

www.zautomotive.com

guruman · Mar 19, 2023

Robr651 said:
Electronic lockers are an issue on the JL’s and Tazer came out with these to fix the issue:

Z Locker OEM – Z Automotive

www.zautomotive.com

I'm not sure I'd call this a "fix". I mean, I'd buy one if I needed it, but....

I understand the issue to be with the locker sensor (that tells the Jeep if the locker is engaged or not), rather than the actuator (that actually engages the locker).

The issue is that if the locker and the sensor status do not match, it throws an error. I don't know if the issue was improper installation or a bad batch of parts, but the replacement part is on backorder forever.

Tazer made this kit to lie to the Jeep computer. It just tells the computer that the locker is in the correct state, regardless if it is or not. As long as the locker is working properly, that's not an issue. But if the locker sticks in the engaged position, you might get some unexpected results before you realize that the locker is still engaged.

Robr651 · Mar 19, 2023

The sensors get gear oil in them and fail. It seems that it would be an easy fix to just replace them but they’re not available (like many parts these days).