Serv 4wd - U0403-00 & C1403-15 Transfer Case Errors - 2018 JL Unlimited Sport S

KevinJL18

New member
Short story:
Does anyone know which harness connects the transfer case range position sensor to the battery - 2018 JL Unlimited Sport S w/ V6 - 8 speed auto? Additionally is this something that can be replaced by myself or do i need to bring this back to the dealer to work on?

Longer story:
So I've had some issues with my 2018 JL unlimited sport s recently - Battery light came on and dash read "battery saver on", along with the "Serv 4wd" light. Didn't know what either were, but drove for about 20 miles and the electronics went completely haywire - radio turning on and off, wipers and defroster both activated, transmission went into neutral, and then just shut down. Long story short, after unsuccessfully jumping the car and getting a tow to the dealer, the service guys came back and said that rodents had chewed up my alternator harness. Dealer went ahead to replace that which seemed to do the trick - car has been running great, no battery light or anything.

However... the Serv 4wd light was still on. I tried to pop it into 4wd and I was unable to do so. I mentioned to the service attendant at the time when i picked the car up and he ran diagnostics and U0403-00 & C1403-15 popped up, which read "Implausible Data received from T-Case" and "Transfer Case Range Position Sensor-Circuit Short to Battery or Open"

I didn't have time to leave the car with them to continue to work on the car, so I thought i'd do my own due diligence to see what the issue could be. After looking at the wiring diagrams, it seems that the alternator harness is directly next to the transmission/transfer case harness.

I haven't had the chance to look under the hood to see if there is any other damage, but considering the evidence it seems likely that the rodents got to that harness as well. However, my has brought me to a standstill - i cant seem to find the correct part for this wiring harness. Does anyone know which part this could be? Also, is this something that could be worked on at a home garage with jacks or do you think it would be worth it to just let the dealer handle it and bite the cost of labor?

Any help or previous experience with a similar issue would be appreciated!
 

unaseer

New member
I had the exact same thing happen with my JL. The dealership told me that I needed to replace both batteries and a fuse. It's all bullshit in my opinion. They know JLs have electrical issues and instead of being honest about it they throw money and parts at the problem. My JL still throws random warning lights but I will not go back to a dealership again.

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jayp2991

New member
I had the exact same thing happen with my JL. The dealership told me that I needed to replace both batteries and a fuse. It's all bullshit in my opinion. They know JLs have electrical issues and instead of being honest about it they throw money and parts at the problem. My JL still throws random warning lights but I will not go back to a dealership again.

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Hello same issues so how do resolved the problem
 

brennaman

New member
Not sure if this is the same problem that I had with my GC, but it is worth looking at. On the transfer case, there is a connector that is used to read if the transfer case is in 4H, 4LO, N or 2W. being down close to the ground, water got in the connector. At first the problem was a random problem, when it was wet out. After a while, the pins corroded and that is how I found it. Once the problem was constant, I was able to track it down to a connector. I cleaned it up and put a dielectric grease in there and it has been fine for the past couple years.

My JL is still on order, so I can't go out and look at it. You should have the same transfer case, the NV241 (unless you have the Full time 4-WD system, I think it has a different transfer case) Good luck
 

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