Battery Voltage Problem?

[ffward]

I appreciate all of the advice and information. Using all of that, I will be able to spend some time and dig down deep into it this weekend.

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[ffward]

Update: After being able to spend some time on it this weekend, I was able to determine that the Aux Battery was the problem. Good a new one and everything is working great now. I appreciate everyone's help and advice. This is the first vehicle I had that has had ESS, Aux Battery, and AGM Batteries. I learned a lot about all of these as compared to a "traditional" "old school" 12 VDC system. Thanks for the help.

 

[Gossamer]

My 2020 Gladiator would not start yesterday. The voltage on the Jeep's info screen said 11.4 volts, yet my muti meter read 12.5. I used my small jump starter and the jeep started right up and the info screen read 14.4. After driving for about an hour, I got home and tuned it off. I checked the voltage on the multimeter and it read 12.5, and this time the info screen voltage read 12.5, and it started right up. It sat overnight, and now it is doing the same thing where the multimeter reads 12.5, but the info screen reads 11.4, and it will not start. Started it with my jump starter and both the multimeter and info screen read 14.4 again. Any ideas, suggestions on what could be going on? Thanks.

had a similar issue. Turned out to be a faulty harness on the drivers side door Where you plug/unplug to remove the doors. Kept showing a voltage and also charging issue for the start/stop system. 3 trips to dealer before they found it. Good luck!

 

[Geoarch]

This diagram (that I found by search) seems to answer all the start questions except what signals the stop/start, i.e., triggers the PDC relay. The PCR is normally closed netting both batteries hooked together in parallel. The PCR opens when signaled by the truck system that the truck has stopped. Does this mean that when you crank the vehicle in the morning that only the main battery is connected?

Very helpful, thanks.

 

[ShadowsPapa]

except what signals the stop/start, i.e., triggers the PDC relay. The PCR is normally closed netting both batteries hooked together in parallel. The PCR opens when signaled by the truck system that the truck has stopped. Does this mean that when you crank the vehicle in the morning that only the main battery is connected?

Not sure if this has been said or not - rather than reading the whole thread again -
No, as said before, the PCR is closed at all times, even during cranking, and open only for a very brief time during a cold start to check the aux battery voltage, and then during an ESS stop event. It's only open to keep the batteries independent, disconnected from each other, so that the crank battery is not drained while the engine is off during an ESS stop.
It's connected again when the ESS stop event is over and the engine cranks to start it.
So two times it's open -
Short time during cold start for a quick battery voltage test of the aux battery
and
During the time the engine is OFF during an ESS event.
At all other times it's closed.

 

[ShadowsPapa]

had a similar issue. Turned out to be a faulty harness on the drivers side door Where you plug/unplug to remove the doors. Kept showing a voltage and also charging issue for the start/stop system. 3 trips to dealer before they found it. Good luck!

That harness can cause all sorts of freaky things - depending on the connections within that are compromised, or the combination of connections that are compromised.
Remote start won't work if it thinks the door is open, for example. It may refuse to move, give errors about shifting, and quite a few other things I've observed over time here.

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