Need help diagnosing issue

[JeeJeep]

Hi All,
So my 2018 JLU with 8k miles started acting up within a month of the warranty expiring ?.

One day back in July it just didn't start out of the blue, took it to the dealer, AUX battery was dead, had it replaced. They tested the main, said it was fine.

3 months later, the radio screen just went dark (music still playing). Got it back on somehow. Two days later, Jeep won't start again. Main battery reads 4 Volts. Tested it, it was still good (cells etc) just depleted. Jumped the car, it started on the second try but ran with a sort of "electrical sputter", the second I turned the steering wheel (while still in P), it shut off. Repeated twice, same thing, when I turn the steering, the engine shuts off. Turning the steering wheel felt odd, almost like the power steering engaging & disengaging(?). Check engine light on. Parksense disabled.

Tested alternator, read 14V. Fine. The main battery was obviously still very low when the car was running, but it should've been running off the alternator at this point so that shouldn't matter right?

Has anyone experienced this type of shut-off? Any ideas what could be causing the intermittent battery drain?

I have (and have had since day 1) a Tazer that has not caused any issues except for a persistent tire pressure light (still haven't figured that one out either - suggestions welcome here too). However a few days before the AUX battery died in July, the shop had swapped out the Tazer Mini I had for a module that looks the same but had a "Hemi" badge on it without the Z Automotive Logo in an effort to fix the persistent tire pressure light. Any chance that could have had something to do with it?

Apologies for the long post & thanks in advance for your help

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[HiJinx69]

You should replace the main. Obviously it doesn't hold a charge and the alternator can't keep up. I replaced the Aux only on mine and held off on the main, because the voltage was still good. But it failed to start on multiple occasions. I replaced the main and all is good. Mine is an '18 is well and both were the original batteries.

 

[Sean L]

In addition to new batteries, check the fuses, especially the high amp fuses.

 

[Bill_P]

Shutting off when you turn the wheel sounds like a wiring harness issue, maybe something shorting to ground. I know there is a problem with a wire bundle in the front end that rubs and causes electrical problems. There are threads on here about it if you search. The fix is to reroute the bundle I believe, and fix the rub through of course.

 

[Gregj]

Shutting off when you turn the wheel sounds like a wiring harness issue, maybe something shorting to ground. I know there is a problem with a wire bundle in the front end that rubs and causes electrical problems. There are threads on here about it if you search. The fix is to reroute the bundle I believe, and fix the rub through of course.

The power steering pump is electric and has a high amp draw, if his battery is dead the pump turning on will be enough to drop the voltage and shut the engine down.
Gregj

 

[Bill_P]

The power steering pump is electric and has a high amp draw, if his battery is dead the pump turning on will be enough to drop the voltage and shut the engine down.
Gregj

Thanks. I didn't realize it had that much draw on the electrics.

 

[58Willys]

Sounds like your main and possibly your aux batteries are toast. Charge and load test both batteries individually. Replace if either fails. As the JL batteries are connected in parallel, always replace both batteries, as one bad one can cannibalize the other good one.

 

[JeeJeep]

Thanks. I didn't realize it had that much draw on the electrics.

Same. Thank you

 

[rohdawg]

the shop had swapped out the Tazer Mini I had for a module that looks the same but had a "Hemi" badge on it without the Z Automotive Logo in an effort to fix the persistent tire pressure light. Any chance that could have had something to do with it?

I’m surprised no one’s asked about anything about the mystery module.
They removed your Tazer Mini and swapped it out with something you can’t identify?
Did they tell you anything about it?
Did they unmarry your Tazer correctly?

A Tazer that hasn’t been unmarried can potentially cause glitches, but if your Jeep is an ‘18 with the original batteries, I’d put money on that.

Got a picture of the module the shop added?

 

[JeeJeep]

You should replace the main. Obviously it doesn't hold a charge and the alternator can't keep up. I replaced the Aux only on mine and held off on the main, because the voltage was still good. But it failed to start on multiple occasions. I replaced the main and all is good. Mine is an '18 is well and both were the original batteries.

Thanks. Good to know. I guess these batteries only have a 3 years life. Can you recommend a better aftermarket main battery?

That said, I'm still perplexed by how it was fine for 3 months then just went all the way down to 4V seemingly overnight. I was told the main is still healthy, just low. Trickle charging now to see if it'll hold charge.

 

[JeeJeep]

In addition to new batteries, check the fuses, especially the high amp fuses.

Will do, thanks

 

[JeeJeep]

i

Shutting off when you turn the wheel sounds like a wiring harness issue, maybe something shorting to ground. I know there is a problem with a wire bundle in the front end that rubs and causes electrical problems. There are threads on here about it if you search. The fix is to reroute the bundle I believe, and fix the rub through of course.

Interesting.. will have that check, thank you

 

[JeeJeep]

The power steering pump is electric and has a high amp draw, if his battery is dead the pump turning on will be enough to drop the voltage and shut the engine down.
Gregj

That makes sense, thank you.

 

[JeeJeep]

Sounds like your main and possibly your aux batteries are toast. Charge and load test both batteries individually. Replace if either fails. As the JL batteries are connected in parallel, always replace both batteries, as one bad one can cannibalize the other good one.

I read that you were supposed to replace both batteries when one dies, however the dealer assured me that only my AUX was toast when I took it to them in December after load testing each separately. The AUX is still under warranty thankfully.

 

[OhioJeeper]

Thanks. I'm just perplexed by how it was fine for 3 months then just went all the way down to 4V seemingly overnight. I was told the main is still healthy, just low. Trickle charging now to see if it'll hold charge.

If it's a 5 year old battery, that's about it. There's a button on the dash that turns off the radio screen. (probably for night driving)

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