Totally screwed: Installed new Auxiliary Battery and now truck won’t start with multiple errors

[Papa Bear]

Ground G907a has a service bulletin on it for u0121. It is the ground for the ABS module and the PDC. There is also another service bulletin on ground G907a for multiple U type codes.​

S2208000025​

S2208000085​

I checked this out. The diagram shows this ground connects on driver side body behind the driver side front fender. This connection was tight with no corrosion or fraying.

Sponsored

 

[Papa Bear]

ABS Module faults are commonly associated with low battery voltage. I'm still thinking along the line of the battery power or ground connections. Maybe there is another ground on the engine or transmission that is loose.

Any idea where I can find a diagram of the grounds on a 2020 JTR? If so, appreciate you letting me know where to find one.

 

[Vtur]

The starter SW supposed to provides the RF hub with the positioning info (Acc,Run). It sounds like the RF hub doesn't know that the starter SW is in the RUN position. Therefore it can't send a command to the BCM to shutdown the engine. Do you know anyone with a JT or JL to try out their starter SW?

Edit: The starter SW should power on when you open the door and enter the truck. It'll read and send the fob info to the RF hub. The hub then authenticate if the fob belong to the truck, it then send a command to the BCM to start the engine. Once started it, the starter SW send a position state (Run) to the RF hub. This is how the hub recognize the next press of the SW to shut it down.

There's a safety emergency shutdown by press and hold the SW for 2+ seconds.

 

[Killroy Was Here]

Any idea where I can find a diagram of the grounds on a 2020 JTR? If so, appreciate you letting me know where to find one.

This post might help with what you are after:
https://www.jeepgladiatorforum.com/forum/threads/list-of-chassis-grounding-points.27525/post-713458

Dave

 

[Lost1wing]

I

Any idea where I can find a diagram of the grounds on a 2020 JTR? If so, appreciate you letting me know where to find one.

See someone hooked you up with the answer. I've been busy with grandkids so a promt reply was missed.

 

[Hootbro]

Any idea where I can find a diagram of the grounds on a 2020 JTR? If so, appreciate you letting me know where to find one.

 

[Papa Bear]

I appreciate this data on the grounds. I'm going back in to dealership this afternoon so they can have my truck all day. I have read on the JL Forums that there is an issue with the Star Can Bus and also ShadowPapa has pointed this out previously in other posts. The dealer never went through that because it is time consuming and requires more experienced techs but they have promised me to go through that system as well. One other side note, the auxiliary battery system has been prone to cause a lot of electrical issues some similar to mine. Has anyone had an issue that turned out to be related to a problem with either a new auxiliary battery that was faulty or anyone of the systems that are powered by the auxiliary battery that had symptoms similar to what I have described? I just want to put together a playbook for the dealer in case they are stumped yet again. The last inspection they had was not able to reproduce the issues so they said that updating the software should fix the issue...it was symptom free for 700 miles but, alas came back three times since then.

 

[ShadowsPapa]

They did "go through" the star connector area on mine last November or so, but last week, I got the MIL again and a real quick list of bus/communication/not responding error codes. Of course, after 2 stops on my errands, it cleared itself and nothing was stored.
I'll talk to them about it again when it goes in for the broken body bolt (and something else now I can't recall what it was.......)
If it continues after that, I'll pick a day and pull things apart and look over every connector with a magnifying glass and light (used to be I could read dates and mint codes off old coins with no magnifying glass - not any more)

If the aux battery was bad, unless it had a short, there should still be 12 volts at the N1 terminal to power the electronics via the main battery. Only if it's bad in such a way that it pulls the main battery down as well would it not function correctly, but then it would likely not start, either.

My first thoughts are along the area of the star connector between firewall and glove box. Especially since it's not constant. A battery issue should be every time, especially after it sits a couple of days. But the connector issues are extremely intermittent - at least in my case. It's happened one time in several months and prior to that it happened 2 or 3 times in 4 months.

 

[Papa Bear]

I don’t know if the Star Can Bus banks were replaced on yours but I just had mine replaced today and I’ll report back to update if that fixed the issue. My dealer said 35 codes were present and they all were fine after new Can Bus installed!

 

[Eric Kern]

Anybody ever get a definitive answer on this? Add me to the list, dash lights up like a Christmas tree intermittently. Usually clears itself after a few drives. U0121 & U0401 confirmed with about 5+ other “U” codes pending…that’s just with a cheap little WiFi code reader. The first time It happened I had my Tazer hooked up to It so I was able to sort out other codes originating from DASM, TCM, and ABS as well as the 8 codes from PCM.
Also usually see an ABS light, “Service Electronic Stability Control”, “Start/Stop Unavailable”, traction control light, CEL. Almost every time after I restart the vehicle only the CEL remains.

Tracked down the G907A TSB on the NHTSB website. The ground looked fine, didn’t have a chance to remove It and clean It up, hopefully tomorrow.

Any and all help is greatly appreciated!!

Sponsored