JL will not start - with pics - need help!

[JohnA]

Hello all, new to the forum and my name is John. I recently installed a mopar auxiliary switches in my jeep JL. I had the battery disconnected for two days. When I hooked everything back up the jeep would not start. The Windows, lights, and radio all work. I took both batteries out amd went to have them tested. Both are fine. It is driving me insane for the last couple days. I just bought a taser to try to clear the CEL’s but no luck. I attached some pics of the dash. Any advice? I checked all the fuses and grounds.

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[WranglerMan]

Silly question but have you checked all the fuses, if you were in the PDC box you may have bumped a fuse loose and it also possible when you were hooking the battery connectors one got shorted and you popped a fuse

 

[JohnA]

I have multiple times. I also checked that the front nuts are all tight.

 

[JohnA]

I checked some fuses to see if the did pop. Are there some I should be looking at that I may not have?

 

[JohnA]

Just checked everyone. They are all fine and non are blown.

 

[WranglerMan]

My guess is it’s the aux battery, I know you had it tested but the JL at least on the 2018’s has to see the aux at a certain voltage to start.

Even though you have dash lights etc. if there is an issue with the aux it will not crank

 

[JohnA]

This is what the small battery read

 

[Gee-pah]

My guess is it’s the aux battery, I know you had it tested but the JL at least on the 2018’s has to see the aux at a certain voltage to start.

Even though you have dash lights etc. if there is an issue with the aux it will not crank

Will: great point.. is the vehicle a 3.6L...and OP does report it being a 2019 where either battery can crank the engine....as you know...

 

[JohnA]

It is a 3.6 2019. I replaced the big battery but same result. Even though the smaller is under voltage it should still want to crank. It was working flawless till I discontented the battery for two days.

 

[WranglerMan]

The ESS battery has to be at the correct charge, the JL looks at the charge on that battery and cranks off the main, you can jumper across N1 to N2 and disconnect the ESS negative that’s attached to the main negative and if its got a good charge it should crank the engine and the Jeep is using just the main battery for checking

 

[JoeBelt]

This is what the small battery read

That battery is almost dead ~40%. Charge it to 13V and try again.

 

[Gee-pah]

The ESS battery has to be at the correct charge, the JL looks at the charge on that battery and cranks off the main, you can jumper across N1 to N2 and disconnect the ESS negative that’s attached to the main negative and if its got a good charge it should crank the engine and the Jeep is using just the main battery for checking

@WranglerMan -- some things are being said here that I think may lead to the wrong diagnosis.

Because the OP has a 2019 3.6L, if he has an ESS/Aux battery whose voltage does not meet the pre-crank test, the vehicle should throw and error code, and subsequent attempts to crank should occur off the main battery--that's provided the wiring is as per factory and the rig's logic is working.

If this were a 2018 3.6L that was un-flashed, I would concur...a dead ESS/Aux battery, short of such wiring changes you suggest, would not crank, even if its main battery where in pristine condition for that model year.

I'm not saying his ESS/Aux battery isn't in need of replacement, but if his 2019 has no errors in its logic or wires, your wiring suggestion, while not wrong or ill-advised per se, won't do any more for him getting cranked than what the vehicle can by itself.

There is a difference and implications between your wiring and factory. Your wiring permanently bypasses the ESS/Aux battery, while the 2019+ 3.6L JL merely bypasses the ESS/Aux battery until it's replaced with a working one and the error code is cleared. With your wiring, one should not run ESS. With the wiring left as is, once the battery is replaced and the error code is cleared--and any other problems resolved, running the ESS on or off is okay.

OP: rather than waste more forum space on why....if it interests you I can link you to explanations. It does not make sense that your ESS/Aux battery is your sole problem.

Another thing, at rest, without Will's wiring change, the two batteries are connected in parallel. It is *possible* that your ESS/Aux battery is defective, losing charge, and stealing power from the main battery, which is otherwise fine. This is the nature of two batteries hooked up in parallel. The weak one can steal power from the good one, and if the weak one is unable to effect the chemical processes to store that power, it can be sent off to to black hole where neither battery can use it.

 

[jeepdabest]

I have multiple times. I also checked that the front nuts are all tight.

Whew! That had to really hurt!

 

[Jebiruph]

Based on the symptoms you describe, this doesn't seem to me to be a battery issue. I would say disconnect both batteries for awhile to see if that clears the issue, but it looks like you did that when you took the batteries to be tested. My guess is that it's PCM related systems that are having issues. I also may have seen similar auxiliary switch issues posted. I would search for auxiliary switch issues and how to rest the PCM.

 

[Faresalsal]

I had this issue at around the same mileage as you, the dealership replaced both batteries and something called "z fuse array" (Pictures Below) Mopar part number also pictured below, ask them to specifically check this thing. this part is located on the side of the fuse box with around five wires going on top of it.

my issue was very similar to yours, jeep just wouldn't start, after multiple tries it did and then the whole dash lit up with all sorts of warnings.

Dealership told me this is a known issue and that it is the main reason why the smaller battery dies.

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