Car won’t start

[willysgreys13]

I have a 2021 Willys and last week the car just died. We jumped it and it’s been fine as long as I drive it for more than 5 minutes. Yesterday, it died again even though I drove it for about an hour. We jumped it and this morning, dead. The battery has been checked twice and it’s fine. I’ve been reading that perhaps the aux battery is the problem but no error messages have been popping up. My alternator has also been checked and is fine. Could it still be the aux battery or another issue?

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[Bulletbill]

You’re going to get beat up for the use of “car.”

Aside from that you may have an aux battery issue. It could be the alternator, but that isn’t very common. Is it still under warranty?

 

[Reinen]

You need to replace both Main & Aux.
If you only replace one you will soon have battery issues again.

 

[willysgreys13]

You’re going to get beat up for the use of “car.”

Aside from that you may have an aux battery issue. It could be the alternator, but that isn’t very common. Is it still under warranty?

No unfortunately not. It’s a 2021 but I’ve put 48k miles on it already.

 

[willysgreys13]

You need to replace both Main & Aux.
If you only replace one you will soon have battery issues again.

What do you know about just getting rid of the aux? I’ve seen a couple videos/threads of people removing it.

 

[SmallCrawler]

This seems to be the day for starting/battery issues so I'll just paste my reply to a similar question from earlier today here. I too have a 21 (built in Oct 2020) and just replaced my batteries before getting stranded...

If your 21 Jeep is equipped with a main and auxiliary battery, and those batteries have not been changed since new, then you will likely have to get some new ones installed. Just about all modern car/truck batteries have a shelf life of about 3 years now due to parasitic drain from engine computers/sensors etc.

There is a lot of helpful information on this forum about the goofiness of the small aux battery buried behind the front passenger fender, how to bypass or delete it, and so on. But I have made peace with the design and simply press the electronic stop start (ESS) button to off almost every time I get in the jeep.

From time to time I then monitor the aux battery by scrolling through my center dash information cluster to check on the status of the ESS function. You will know that the aux battery is about finished when you see messages that say it is not ready (when you know it should be charged due to long trips or charging attempts with a battery charger).

Best description I have seen on the forum is to consider the 2-battery factory design, if you have it, as similar to a TV remote. Change both batteries, not just one or the other. It's a goofy design for sure, but it generally works, and all the electronics play nice if you maintain it.

 

[Reinen]

What do you know about just getting rid of the aux? I’ve seen a couple videos/threads of people removing it.

After reviewing the JL wiring diagram I've concluded that the Aux delete accomplishes two things.

1. Makes it so the owner doesn't need to learn the nuances of how a two-battery system works.
2. Makes the Electronics & Communication Network significantly more vulnerable to failure during engine starts.
3. Changes the first warning of battery failure from a non-critical failure (ESS refusing to engage) to a critical failure leaving the Jeep inoperable.

In short, the approach works fine until it doesn't. Which will happen sooner and more severely.
I will not do an Aux delete on my JL. It's there for a reason.

 

[Buzz11]

My guess (like most of the responses) is the AUX battery. Mine just died, no warning, no error codes. I was at the gas station, and it wouldn't start. I pulled fuse 42, and it started right up. Got me home and around until I got new batteries. ... and put fuse 42 back in.

As a side note it takes 60-90 min to get to the AUX battery if you come in from up top.

 

[ParadigmDawg]

You’re going to get beat up for the use of “car.”

Aside from that you may have an aux battery issue. It could be the alternator, but that isn’t very common. Is it still under warranty?

I was about to say, "you should have bought a Jeep vs a car".

 

[Heimkehr]

The battery has been checked twice and it’s fine.

A battery's resting voltage can appear acceptable when tested in isolation. However, it can then fall off a cliff when a starting event (i.e., cranking demand) occurs.

Do give some thought to replacing both batteries at the same time, and use AGMs when doing so. Removing the small ESS battery from the equation is generally well-regarded in the owner community, too. There are several forum threads on the subject that will provide additional intel to assist you in the decision process.

Note also that the Wrangler's powertrain warranty is 5 years or 60K miles, whichever occurs first.

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