Hello,
My name is Frank.
I'm new to this forum. I have a 2008 Rubicon JKU and I'm having weird electrical issues. The truck will run OK, then suddenly run rough and shut down. The odometer will flash and go blank as this is happening and then sometimes will flash "hot oil" The the electric throttle control, check engine will illuminate and then all idiot lights go on and the truck dies...
Tranny fluid and engine oil are OK and clean as are all battery connections. As an FYI, the tranny was professionally rebuild about 3 yrs ago.
I just pulled the following codes:
-C121c: Torque Request Signal Denied
-u0100: Lost communications with ECM/PCM
-u0101: Lost communication with TCM
-u140e: Implausible vehicle configuration data
-c2202: VIN mismatch

I do 95% of the work on the truck, there are no electrical modifications aside from a winch, the computer and all electronics are original.

When I research the codes, the possible causes are all over the place.

Any ideas?

Much appreciated

Frank

 

I would have your battery checked. The JK will sometimes do some quirky things with a dying battery. Also, double check the ground wire to your battery on both ends, as well as the ground straps. There is one running to your hood I believe, as well as one running down to the block. If they all look good, you may be dealing with a bad PCM.

 

Also be sure to check that all connections into the PCM are fully seated with no broken wires anywhere.

 

OK THANK YOU! The ground strap from the hood, to the firewall to the block is shot. I found it about 6 months ago while changing injectors and when I tried to order a new one the auto parts guys said it was dealer only and the dealer parts guy said it was no longer available but that it's just to prevent engine noise from impacting the radio. I can't get to the stud on the block without dropping the pipe at the manifold, so I'll start by rerunning a new wire to another ground point on the engine, then to the PCM ground. I'll check for continuity between the block and the alternator bolt, that would be an easy fix. I'm running a 3 yr old Optima Yellow top that tests OK, I removed all cables to both battery posts, cleaned all contact surfaces and coated with a little dialectic grease.

I'll let you know if rerouting the ground works

Thank you for the guidance.

Stay well Frank

 

Just an FYI - all U Codes are Canbus related. You need a diagram for Canbus routing. I do know that there is one Canbus from the gauge cluster to the TIPM as that is what I chopped into to do my Chev conversion. But I agree with the battery issue mentioned already. Di-electric means 'insulator'. Your terminals should be squeaky dry and clean then coat with Dielectric after the connection is made. I use carbon black grease for contact coatings. Messy and black. Best ever coating for battery terminals is dry and clean again, then spray paint with your color of choice. Yes spray paint.

 

Thank you Jsukey and Sixty4x4,. I think I have it resolved. It was a combination of a bad ground at the battery and a broken battery clamp bolt. The bolt was broken at the retaining clip so it looked like the battery was secure but in reality it was moving around when driving on the local dirt road. This would cause the negative terminal connection to loosen. Replaced the bolt, both battery terminal connections as well as the ground strap. Also thanks for the advise in the terminals. I've been using dialectic grease on bulb connections for years. I'll try your suggestion about the terminals and paint. Have a 3 day off road trip to Pennsylvania with my sons in about 2 weeks (both in their 20's, both own identical 2000 xj's) so I'll be stressing the repairs to ensure i didn't miss anything...

THANKS AGAIN!
Stay well
Frank