2018 JLU wouldn't start

[Rogue321]

Had a strange issue happen today. I pulled into a gas station for a break. Jeep sat there for 15-20 minutes or so. I got in to start it, and it sounded like the starter would just randomly bump, but not crank. The dash lights and gauges was doing all kind of stuff. I kept trying and after several attempts, it started (cranked perfectly once it cranked). I turned it back off and tried it again and pretty much the same sequence.

It did start the second time as well. I drove it a little ways down the road and parked it. The ESS light was on, the outside temp gauge read 150 degrees, and a single red dot lit up on the tachometer. I have no idea what that light was. It doesn't show up when I am in accessory.

I left it there for a bit and came back a few hours later to see if I could get it started to get it back home. Started fine. I turned it off and started fine again. I drove it home, turned it off, started fine again. ESS light is on, but everything else seems fine.

I'm guessing it's probably one of the batteries, but once it cranked, it cranked normally. Cranks normally now.

I'll try to get it into the dealer tomorrow, but curious if any have experienced this, or if there's a tech bulletin describing this behavior.

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[Old Dogger]

It’s probably, just needs the batteries replaced. Are the batteries the original ones?

 

[58Willys]

Batteries dead, or fuses not seated.

 

[Rogue321]

It’s probably, just needs the batteries replaced. Are the batteries the original ones?

I can't say for certain, but I bought it with 32k miles, so I'm guessing they are both original.

 

[Rogue321]

Batteries dead, or fuses not seated.

Any particular ones to look at? This is the first and only time it's done it. Starts fine right now.

 

[rohdawg]

If the batteries are the originals that came with it from 2018, they’re shot.
Make sure you replace BOTH… no matter what the dealerships tells you.

 

[Rogue321]

If the batteries are the originals that came with it from 2018, they’re shot.
Make sure you replace BOTH… no matter what the dealerships tells you.

When one or both of these batteries fail, how do they act? This was such a weird fault that didn't act like a weak battery. Well, I guess it did at first, but then acted normal. It was fairly chaotic when it was acting up, then cranked fine, and is cranking fine now. I know this new tech kind of negates the ways of old, so just kind of curious.

I had no indication of a weak or failing battery. I was in a parking lot and all of a sudden chaos ensued, and then it cranked fine.

And I don't even know what to make of the 150 outside temp. I'm sure it was just an error, but part of me wonders if there was something much more concerning going on. I mean, seems such a strange error. Do you know where the outside temp sensor is located?

 

[rohdawg]

When one or both of these batteries fail, how do they act? This was such a weird fault that didn't act like a weak battery. Well, I guess it did at first, but then acted normal. It was fairly chaotic when it was acting up, then cranked fine, and is cranking fine now. I know this new tech kind of negates the ways of old, so just kind of curious.

I had no indication of a weak or failing battery. I was in a parking lot and all of a sudden chaos ensued, and then it cranked fine.

And I don't even know what to make of the 150 outside temp. I'm sure it was just an error, but part of me wonders if there was something much more concerning going on. I mean, seems such a strange error. Do you know where the outside temp sensor is located?

The two batteries are hooked up in parallel in the 3.6L, including when the rig's at rest and no alternator is running. So one battery is stealing power from the other. It’s usually (as reported by many forum members) the ESS/Aux battery doing the stealing.

You can look around the many threads on the forum and they all say the same thing. No sign of impending doom and than chaos on the dashboard, won’t start, restarts fine and then craziness again… often times leading to complete failure and a stranded Jeep.

Like I said, if those are the original batteries they are most definitely at the end of their life cycle. I changed both of mine (also a 2018) earlier this year and I’d bet I was pushing the envelope. Lol

I wouldn’t make much of the temperature. Probably part of the dashboard freak out. And honestly, I haven’t looked for the ambient air temp sensor. I’m sure someone smarter than me knows where it is.

I hope everything works out for you and it’s as easy as swapping batteries.

 

[AnebuR]

Aux battery is likely shot. First off, make sure you have TSB 18-092-19 completed (Power Control Update), since yours is a 2018 and is affected. It will decouple the aux battery from the starting process. Otherwise, you won't be able to start even if your main battery is fine if the aux goes. Second, you can bypass the aux battery completely without needing to replace it. Just remember to press the button to disable the ESS every time you start your Jeep if you do this: https://www.jlwranglerforums.com/forum/threads/jumperless-aux-battery-bypass.95945/

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