Remove Auxiliary Battery

[AndySpill]

This is a wild ass guess, but since the running lights are controlled from the cab, I'd say they are running on the aux battery during a stop/start event.

That would be my guess too.

Some appliances do seem to run only on the main battery, but perhaps don't normally require power during an ESS event, like the power steering.

https://www.jlwranglerforums.com/forum/threads/drained-battery-any-jumpstart-tips.12316/post-981215

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[nositting]

Success, 90% level. Did the 2 most straight forward, least OEM modifying steps.

• Disconnected the AUX batt NEG cable end at the Primary batt.
• NOTE: On my JLU Sahara 2018, the AUX batt NEG cable end was attached to the extra post on the Primary batt NEG cable end. Beware, a YouTube video shows exactly opposite.
• Pulled F42 in fuse box.

The 10% NOT success is my center dash behind the steering wheel shows the ESS disable warning symbol. It is immediately above the top of the fuel level bar. The actual ESS button switch on the center console appears to work as normal. Start up is OFF, during run time pushing the button switch turns button indicator light ON. And second push turn button indicator light OFF.

The 90% SUCCESS is the ESS is disabled at start up and remains so. And the Dash Screen that shows the ESS system reports the ESS system is disabled or OFF.

So, not sure what pulling the F42 fuse actually does.
I could re-seat the F42 fuse and have the same result?

sounds kind of like my situation….
- 2019 3.6 with 90,000 miles.
- no fuse 42 for a couple months.
- negative from aux pulled and taped up (the smaller of the two negative cables) for a couple months.
- stop/start avenger symbol lit up on dash which occurs if button is pushed or not.
- no functioning stop/start at traffic lights.
- new AGM H7 as of 8/22.
- 12.5V engine off, 12.7V acc on, 14V upon start up.

no problems yet.
haven’t bought stop/start eliminator or tazer and, not sure if i will. i haven’t removed aux battery but probably will this summer the next time i rotate the tires.

if anyone sees any issue with any of the above, feel free to chime in.
thx!

 

[THAW]

since the running lights also stay lit during an ESS event, *something* has to be powering them too; would that be the Main batt, or the Aux batt?

This is a wild ass guess, but since the running lights are controlled from the cab, I'd say they are running on the aux battery during a stop/start event.

That would be my guess too.

There's no reason to guess; you're both correct.

The AUX (ESS) battery is directly connected to the PDC (fuse box), and therefore nearly every electrical component. The CR[an}K (main) battery is directly (i.e. without a switch, namely the PDC) connected to only the starter, radiator fan, power steering, and alternator,

Therefore, with the PDC open during an ESS event, the AUX (ESS) battery powers everything but the radiator fan and the power steering (the operation of either will in most cases prevent/kill an ESS event).

 

[LHSmith]

Got it. Scenario is:

IF [ Disconnect the Auxiliary battery ]​

IF [ ESS button Active ]​

Primary battery must carry electronics load while engine OFF​

ELSE [ ESS button OFF ]​

Primary battery free from engine OFF electronics load​

To clarify:

Disconnecting the Auxiliary Battery NEG wire from the Primary Battery terminal is the only work required to eliminate the Auxiliary Battery operation.​

Pulling fuse 42 is just to stop a warning light on the dash.​

​

Seems only little benefit from physically removing the Auxiliary Battery.

I have a 2018JLU, with the AUX battery cable disconnected and Fuse 42 pulled. No problems starting, However the ESS light on the dash is on, regardless of the switch button?

 

[AndySpill]

I have a 2018JLU, with the AUX battery cable disconnected and Fuse 42 pulled. No problems starting, However the ESS light on the dash is on, regardless of the switch button?

Hi Larry:

Your factory dual AGM battery JL will illuminate this light in the EVIC (dash) when the Aux battery, or what the vehicle thinks is the Aux battery (in your case given your wiring and fuse changes your main battery) is lacking in power.

Is it possible that your main battery is due for replacement?

 

[mbrose1994]

[QUOTE="LHSmith] ... However the ESS light on the dash is on, regardless of the switch button?

Yes, that is what I have too. Which is valid, since the ESS is not active. So, I have no idea what pulling Fuse 42 accomplishes. I also saw a comment that stated the ESS switch button on the dash should be pushed and therefore ON. No clue why or what that accomplishes either.

 

[Aonarch]

Has anyone removed the aux battery on a 2024+? Any differences?

 

[mbrose1994]

Yes, remove fuse 42 in the main fuse box, and remove the negative battery cable for the auxiliary battery. Then tape the removed battery cable end with electrical tape or heat shrink tubing. You may or may not have the ESS light on the dash. I did this procedure on my 2018 JLU, and the dash light is still there?

Yes, did exactly the above. But, after that, "Electrical Storm" still happens intermittently.
Is my 2018 JLU Sahara may be a bad unicorn?

Then, discovered I needed another PCM update TSB: 18-039-22. Which included an ABS upgrade.
Dealer charged over $250 for that. I guess only safety TSBs are free. But how is "Electrical Storm" not a safety issue?

Anyway, less than 50 miles driving, hit with "Electrical Storm" again.
Dealer suggested may be CAN bus issue. I suspect is a honey pot for the Dealer to chase electrical ghosts and do nothing.

What is the next logical step?

 

[mbrose1994]

Discovered the real issue was my CAN bus star connector under the glove box. New part $65, replaced in less than 10 minutes. All the "electrical storm" behavior is gone!

Now I have achieved simple, total, absolute electrical separation from Jeep's Rube Goldburg AUX batt design.
No remove/replace the right front fender.
No remove/reinstall PCM box.

Just disconnect and tape off (electrical tape) all (1 NEG, 2 POS) AUX batt cable ends.
Leave CRK batt POS cable end on N2.
Jump N2 to N1.
Done.
Jeep life is good again.

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