'18 JLUR Electrical issue mystery - Help

[Medictrode]

Hello all,

Recently my JL has been going nuts to the point where it won't allow me to shift into gear, or if driving it won't shift gears. 70+ Codes end up popping up and it appears to be a failure of the CAN bus as many modules throw that same code. So yes, I've googled and also searched here and it seems many have the same issues. I've myself load tested the batteries as well as have the dealer do so, I've disconnected the aftermarket auto start and also have checked for chaffing wires near the bell housing. I've also saved tons of data on various sensors while driving, but nothing seems concrete yet.

I've also hooked up an oscilloscope onto the CAN bus and you can clearly see the bus go below voltage thresholds before the dash lights up and goes nuts with warnings.

I have it at the dealer now and they are also perplexed and just sent me a text saying that the PCM will send multiple codes when it's on the ground but not on the lift.. That is a new one to me, and they are still working on it, but figured I'd ask here to gather as much data as possible. Hopefully someone has something to add that I haven't seen here, or thought of yet. Thank you

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[zrickety]

Hello all,

Recently my JL has been going nuts to the point where it won't allow me to shift into gear, or if driving it won't shift gears. 70+ Codes end up popping up and it appears to be a failure of the CAN bus as many modules throw that same code. So yes, I've googled and also searched here and it seems many have the same issues. I've myself load tested the batteries as well as have the dealer do so, I've disconnected the aftermarket auto start and also have checked for chaffing wires near the bell housing. I've also saved tons of data on various sensors while driving, but nothing seems concrete yet.

I've also hooked up an oscilloscope onto the CAN bus and you can clearly see the bus go below voltage thresholds before the dash lights up and goes nuts with warnings.

I have it at the dealer now and they are also perplexed and just sent me a text saying that the PCM will send multiple codes when it's on the ground but not on the lift.. That is a new one to me, and they are still working on it, but figured I'd ask here to gather as much data as possible. Hopefully someone has something to add that I haven't seen here, or thought of yet. Thank you

If you are on original batteries, they probably need replacing. Even if they test ok. Otherwise I would suspect the alternator.

 

[jludave]

Hopefully someone has something to add that I haven't seen here, or thought of yet. Thank you

Your have a 2018. You are at the point where the OEM/factory batteries lose their life. When one battery goes, the other follows. Failing/old batteries cause all types of weird electrical issues in the JL. Replace your main and aux batteries.

 

[four low]

Aftermarket Remote Start ?? My money is in a bad connection, especially due to the transient nature of the electrical problems. I would uninstall that system, paying particular attention to any splices, added harnesses, and replace both batteries.

 

[Leti_The_Jeep]

Try wiggling the wires behind the glove box, that's where the CAN BUS hub lives, Mine acts up and when I touch the wires, everything goes back to normal. Hell even hitting the glove box with an open hand fixes it some times

 

[jludave]

Try wiggling the wires behind the glove box, that's where the CAN BUS hub lives, Mine acts up and when I touch the wires, everything goes back to normal. Hell even hitting the glove box with an open hand fixes it some times

This is 100% not normal and not a fix. If you need to do this, you have other issues with your vehicle.

 

[Leti_The_Jeep]

Try wiggling the wires behind the glove box, that's where the CAN BUS hub lives, Mine acts up and when I touch the wires, everything goes back to normal. Hell even hitting the glove box w

This is 100% not normal and not a fix. If you need to do this, you have other issues with your vehicle.

100% agree, but knowing its an intermittent connection issue in the cab will help the dealership diagnose the issue a lot faster (spent way to much at the dealership, having random connections looked at for the problem to still persist)

 

[Medictrode]

Thank you all for the replies..

In regards to the autostart, before I took it to the dealer I made sure I disconnected everything. This is mostly due to the fact that once a parts changer at the dealer saw this they would immediately blame it on that, make it the fault of the owner and say it's fixed. Most of these guys don't really have a true skillset when it comes to electronics and will just keep changing parts until it's fixed..

Hence was the case here where they suspected that the sway bar unit/module and the harness going to it was the issue. I knew it wasn't the issue, but I said to go ahead and change that out.

As I suspected, it did not fix the issue. I did change the batteries because yes, they are on the old side. I also found a TSB that stated there could be an issue with the ABS and it's ground point on the drivers fender under the hood.. So I took that off, cleaned it and while in there also hit every ground connection I could find..

With all that said, it's still happening. Sometimes it's worse there others and the power steering will go out when it's doing it's dash freaking out thing, so it's now a safety issue. It will also still prevent me from going into gear when parked and it occurs.

I will check on the CAN BUS junction block as the one poster stated and mess with those wires. I've seen many posts about this and still wondering if anyone could chime in if they had the same issues with their Gladiator or JL, and if fixed, what the fix actually was.. Thank you all for any help.

 

[shotcoach]

I'm having very similar issues, Medictrode. Dealership replaced the ABS module and said it's all good. Less than 20 miles later and the issue returned. My Jeep is currently sitting at the dealership...

Have you had any luck since your last post? Thanks in advance.

Doug

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