Serv 4wd saga continues

[mtu1293]

I've mentioned this in my build thread, but starting its own topic here on the PW forum as well. This is on my 2019 PW
Ever since I've owned the truck (1 year now) I've gotten a random SERV 4WD light that comes on. Mainly when just driving in 2wd, 90% of the time it clears once the truck is shut off and restarted. I've had at least three times in a year where the light hasn't cleared with restart. Of the three times, it cleared with the truck still running. Unfortunately it is out of warranty - miles wise.

Typically hasn't been much of a concern, but it did almost burn me once. I was doing a rescue of two vehicles stuck on a muddy trail, and the light came on. Of course needed 4x4 at the time, so it got a little interesting for a bit. Was backing down a 2 rut trail, and all of a sudden light went away and I got my 4x4 back.


- Does this randomly, mainly when in 2wd. Can be nice out, raining, snowing, warm / cold, driving straight, turning, slow speeds, highway speeds. etc
- Tcase does shift into 4low, but with the light on axle doesn't connect so technically in 2low
- checked wiring connections: made sure they where snapped in and no frayed wires.
- Sometimes goes months without coming on, other times happens multiple times in 1 day.

Few weeks back the light came on while in town 4 times within 30min, so on the way home I swung by the dealer. They where able to check it right then, and the tech said it was giving a tcase fault. I always assumed it was the front axle disconnect motor causing the problem. They wanted to check all the wiring so I scheduled an appointment, figuring I might as well start somewhere. They checked all wiring, and found no definite issues, so they are trying to say MOPAR says tcase not serviceable and to replace at $1800. The one thing they did find was a corded pin on the wiring (crossing fingers that could be it). So they concluded if that doesn't fix it, they say replace the tcase.

Even though there is a tcase position sensor, as well as the electric actuator for front axle disconnect. I still have a feeling it is one of those two, either makes sense in a way. That is if the light comes on again, after cleaning the corroded pin.

Guess mainly just looking for any advice and/or if someone else has had this same problem.

 

[olyelr]

The tcase positioning sensor usually gives an intermittent “4wd shift in progress” dash light when it goes bad, and does not prevent the 4wd from still engaging. So i wouldnt think it is that one.

I would venture to say it is more in the axle disconnect part of the system.

Also, one thing i do know is that if the wheel bearing speed sensor goes bad, for whatever damn reason it will no longer allow the 4wd to engage. Maybe check into that as well.

Good luck and keep us updated !

 

[crazy jerry]

surely i would think theres stored codes. i dont know much about these electrical systems but my common sense says replacing the tcase is a stupid idea without knowing thats the problem. i would investigate what parameters trigger the serv4x4 light.

 

[olyelr]

Yea, replacing the entire tcase would be asinine. Could almost guarantee it wouldnt even fix the issue. I mean, its mechanical and apparently works just fine when the electrical code is not popped up, correct? Why the eff would they replace the tcase?

 

[crazy jerry]

if it were my truck i would already had a service manual because at some point you may need it and it has diagnostic information. next i would dielectric grease the smart bar plug. next i would check for any codes on that light. i wouldnt throw any parts at it yet. you need a code or to know what can trigger the 4x4 light then youll have a direction to look

 

[mtu1293]

When they checked codes it was for the tcase, which was a surprise for me. I don't have that printout to say what the exact code was. They asked if it was hard to put in 4x4, I was like no, it's always been easy to pull into 4high or 4low.

Since they cleaned that one pin, I haven't driven it much, but light hasn't come on. lol - but again the light has gone dormant for a few months before as well. I never got to into it since it was so few and random most of my ownership. Mainly since it almost got me stuck on a trail I started to get a little more concerned.

And yeah there is no way I would have them replace the tcase, and just start throwing parts at it because they can't figure it out. I was just more shocked that they claim the tcase isn't a serviceable item, that its replace only.

 

[BigLazer4u]

My 2019 did all the same things you are speaking of, first they replaced my sensor because it was shifting into 4wd while driving down the interstate.. next they replaced the T Case.. few months later they ended up having to replace my actuators Because my differentials would no longer lock.. of course with tons of error codes.. I also started having the amazing blue smoke on startup from the wonderful 6.4, I sold the PW and bought a Cummins. havent had a problem since. Good luck to you. It appeared to me to be a endless battle and I’m glad I rid of it.

 

[mtu1293]

My 2019 did all the same things you are speaking of, first they replaced my sensor because it was shifting into 4wd while driving down the interstate.. next they replaced the T Case.. few months later they ended up having to replace my actuators Because my differentials would no longer lock.. of course with tons of error codes.. I also started having the amazing blue smoke on startup from the wonderful 6.4, I sold the PW and bought a Cummins. havent had a problem since. Good luck to you. It appeared to me to be a endless battle and I’m glad I rid of it.

See mine just throws the Serv4wd light. It isn't trying to shift into 4by. Not getting much for error codes - need to talk to dealership to see what tcase code the tech mentioned.

At least as of now, when the light isn't on, everything else works flawlessly. Lockers engage quick as well as swaybar.

With fuel prices, I'm swaying to starting using my 6.6 duramax farm truck for more driving duties - lol.

 

[crazy jerry]

i doubt its the tcase itself. but if you have the electric shift version maybe its the motor or a position sensor. the exact code should tell them what it is but thats only if theyre smart enough. a service manual should tell them how to pinpoint it based on that code and diagnostic tree

 

[smittyd174]

Had the same issue with my 2016 , 3500 .Live in Canada and was towing my 5th wheel to Georgia when it started .Service 4wd light came on then off , on, off while driving . Got on the Ram forums and people said the issue was moisture in the axle actuator connection. When I got to my destination , crawled under truck unplugged actuator cleaned with contact cleaner , light spray of wd40 and die electric grease to keep the moisture out . Never had another issue . Always try simple , cheap and easy first , took less than 10 minutes.