Jumperless Aux Battery Bypass

[KoKo]

Thank you to all who have contributed to this thread and related ones!

I had the same issue where both batteries died. Jumpstarting the jeep would fire it right up and had mostly no issues after (aside from the occasional "water in the fuel tank errer") , but as soon as I removed F42 and then disconnected & removed the aux battery the errors went away. The jeep still wouldn't start, but it turns out that this whole debacle ended up killing BOTH my batteries. Went to Auto zone, and they replaced my main battery for free ( 4 months old). After swapping my main Optima DH7 for the new one, I have had absolutely NO ISSUES!

TL:DR

• Both batteries were dead.
• Left everything as is
• Removed F42
• Removed the main battery (to get to the auxilary)
• Removed the auxilary battery and wrapped the +ve and -ve leads.
• Reconnected the New main battery
• ALL ID PERFECT I THE WORLD
• It's been a whole week and have not needed my Jumpstarter!
• *** HAPPY DANCE ***

PS. This is on a 2022 JLU 3.0 EcoDiesel

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[Go Hogs!]

Thank you to all who have contributed to this thread and related ones!

I had the same issue where both batteries died. Jumpstarting the jeep would fire it right up and had mostly no issues after (aside from the occasional "water in the fuel tank errer") , but as soon as I removed F42 and then disconnected & removed the aux battery the errors went away. The jeep still wouldn't start, but it turns out that this whole debacle ended up killing BOTH my batteries. Went to Auto zone, and they replaced my main battery for free ( 4 months old). After swapping my main Optima DH7 for the new one, I have had absolutely NO ISSUES!

TL:DR

• Both batteries were dead.
• Left everything as is
• Removed F42
• Removed the main battery (to get to the auxilary)
• Removed the auxilary battery and wrapped the +ve and -ve leads.
• Reconnected the New main battery
• ALL ID PERFECT I THE WORLD
• It's been a whole week and have not needed my Jumpstarter!
• *** HAPPY DANCE ***

PS. This is on a 2022 JLU 3.0 EcoDiesel

What did you wrap the leads with? Electrical tape or something more significant?

 

[Shellbird01]

So for an early 2018 3.6 n2 post is the main crank (even tho it shows ESS)? So it must stay, yes I have the TSB

 

[KoKo]

What did you wrap the leads with? Electrical tape or something more significant?

Two layers of Heavy Duty (read thick) heat shrink tubing for each lead, then wrapped that with electrical tape...

 

[THAW]

So for an early 2018 3.6 n2 post is the main crank (even tho it shows ESS)? So it must stay, yes I have the TSB

Yes, N2 connects to the CR[an]K (aka "main") battery, and the wiring must be retained.

The parenthetical "ESS" designation in the label "N2 CRK BATT (ESS)*" indicates the location is relevant to vehicles built with the electronic stop/start system (as opposed to "BSG" for eTorque).

 

[Shellbird01]

“Parenthetical” nice! Never playing scrabble with you. Kept the N2 connection, as for the rest, She gone!

 

[ScotM]

Is it possible to do this without taking out the entire fuse box? I am putting in a new battery, and have easy access to the fender with quick release liners. I can get to 1 and N3, but can you access the PCR to remove it without taking out the fuse box?

 

[THAW]

Is it possible to do this without taking out the entire fuse box? I am putting in a new battery, and have easy access to the fender with quick release liners. I can get to 1 and N3, but can you access the PCR to remove it without taking out the fuse box?

Yes, the PCR is on the firewall behind the AUX (ESS) battery box.

[borrowed image]

 

[Jammer]

Couple of the aftermarket shops have told me do not disconnected auxiliary battery. It's made to run with it it's made to charge with it and they have JL rubicon's themselves. They could do it at the same easy way they wanted to and they have it because it meant to charge with the big battery in the little battery I'm not going to worry about it I just buy a new one every 3 and 1/2 to 4 years it's a warranty for 3 years both of them so about every 3 and 1/2 hours behind new one. Texas heat and the winters are brutal on batteries. Rather have fresh batteries every 3 and 1/2 years to be going somewhere one night and get stuck and it won't charge but it's made to run with a silly battery is what the guy told me in a couple shops and they won't do theirs they won't disconnect it sounds good and easy but it can cause you problems

 

[jludave]

Couple of the aftermarket shops have told me do not disconnected auxiliary battery.

Find new shops. They are full of crap. Many, including myself, have been running with the aux battery bypassed for years with ZERO issues. The entire point of this thread and the aux battery bypass, is that the vehicle can run just like any other vehicle with a single main battery.

 

[T-Rob]

Exactly! I deleted my aux battery over 4 years ago with 0 issues. The issues that I used to have when the aux battery was connected have never returned. Our JLs can run on a single battery easily.

 

[ScotM]

Yes, the PCR is on the firewall behind the AUX (ESS) battery box.

[borrowed image]

Awesome, I’m doing that. Thanks

 

[Heimkehr]

the PCR is on the firewall behind the AUX (ESS) battery box.

PCR = Power Control Relay? If so, what's its functioning?

 

[ScotM]

PCR = Power Control Relay? If so, what's its functioning?

Search power control relay on this forum, there is an entire thread devoted to its function. I don’t know how to link it here, sorry. It was on November 24, 2024.

 

[Heimkehr]

Search power control relay on this forum, there is an entire thread devoted to its function. I don’t know how to link it here, sorry. It was on November 24, 2024.

Found it, thanks.

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