My Automatic Stop / Start doesn't work - Wrangler JL 2018

[PLR]

For the past year my auto stop start does not work - not a problem as I don't like it and would normally switch it off - but...dealer said to charge the battery to full - I drove to Spain and back - 2000 miles - still not working - and sometimes the system powers down and switches off radio etc. Battery is nearly 4 years old - should I change it? - and I believe it has two batteries - why??
Thx,
Peter

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[jaymz]

The small auxiliary battery has likely been shot for a year. You’re lucky it hasn’t completely died and left you stranded. It’s time to replace them both. Or bypass the auxiliary altogether if you’d like. Tons of info here to explain the process.

 

[Fudster]

For the past year my auto stop start does not work - not a problem as I don't like it and would normally switch it off - but...dealer said to charge the battery to full - I drove to Spain and back - 2000 miles - still not working - and sometimes the system powers down and switches off radio etc. Battery is nearly 4 years old - should I change it? - and I believe it has two batteries - why??
Thx,
Peter

Jay. I'm lucky I caught you early on this one.

Coming to this forum with this question, which has so widely been discussed, might get the less patient incensed.

Given your willingness to do without the ESS system here's what I think you should do. First, go out and buy a new main battery if your 2018 hasn't had one sooner. In this day and age of crappy AGM batteries, I'd replace mine every 3 years. Links are available on request for suitable substitutes.

Second, I want you to disconnect your smaller ESS/Aux battery, which itself is tucked away out of visibility, using the following method:

First, from the factory there are two black cables that lead to the main battery's negative post. One of those cables finds its other end at the passenger's front quarter panel. It is a body ground cable that you are to leave connected, untouched, as is.

The OTHER cable has as its distal end the negative terminal to the ESS/Aux battery. Disconnect it. Wrap its loose end in electric tape.

Next, closest to the front passenger's seat, under the hood, on top, is a black box known as your Power Distribution Center or PDC. Think of it as your vehicle's intelligent fuse box.

I want you to pop open its cover, locate Fuse 42, and pull that fuse out.

That should solve your problems if not explain the "why" aspect of things. Here's the why:

Your two batteries are connected in parallel (positive terminal to positive, negative to negative) at all times but an instant prior to crank, and during ESS events. Having those two batteries connected means one can cause the other's demise---and usually its the ESS/Aux battery that can negatively effect the main battery.

Pulling that cable I described takes the ESS/Aux battery out of the vehicle's electrical schematic.

But doing so can effect your ablity to crank**. That's where the Fuse 42 pull comes in. Pulling that fuse prevents the batteries from ever being separated in the 2 times I describe. All calls for power from either battery will now go to the main one.

Do turn off the ESS system with a button press or after market tech. We don't want ESS events running with that one main battery because it may rob the main/only battery of cranking power after the ESS event is over. That's what the ESS/Aux battery you just took out of the electrical circuit was for: i.e. to run appliances during an ESS event to preserve the main battery to handle the bulk of the post ESS event crank.

@@@@@@@@@@@@@

**later model 2018 JLs and all model years thereafter with dual AGM batteries will fail after disconnecting the ESS/Aux battery if Fuse 42*** is left in, but should crank on second attempt from the main battery. If successful, the vehicle will automatically take the ESS/Aux battery out of the vehicle's electrical schematic, crank thereafter on the first try and run off the main battery only, and put an ESS off light on in the dash forever more until the next cold crank, if any, where an energized ESS/Aux battery is detected.

The original 2018s though won't crank if the ESS/Aux battery is dead and Fuse 42 is left in. Not unless they have TSB 18-092-19 applied to them by the dealer, in which case they act like the aforementioned newer JLs.

I don't know which 2018 you have. If you have the later model ones or have TSB 18-092-19 you can just disconnect the ESS/Aux battery, attempt to crank, and if you fail, try again against the (new) main battery. This route will turn ESS off for you and run only against the main battery from that point until, as mentioned, an energized ESS/Aux battery is, if ever, reconnected.

But if you don't have TSB 18-092-19, or hate seeing an ESS off light in the dash, pull Fuse 42 and turn ESS off yourself.


@@@@@@@@@@@@

***Fuse 42 controls a relay that if energized, separates the two batteries. No fuse, no relay power. No relay power no separation of the battery cables.

 

[RenegadeT]

A few months ago, I posted a similar thread. Bought my 2018 in 2020 with very few miles on it, and the start/stop didn’t work. I am not a fan of it, so I was OK with it, just a little worried the battery might need to be replaced.
So after about 8 months of regular daily driving, it started working. That prompted me to post on here. A few replies suggested it took that long to recharge the aux battery to a condition where the start/stop is enabled. Now 3-4 months later, the start/stop is always working, and I am constantly to shutting it off. The button is literally right next to the shifter, so it’s not that bad.

 

[txj2go]

Jay. I'm lucky I caught you early on this one.

Coming to this forum with this question, which has so widely been discussed, might get the less patient incensed.

Given your willingness to do without the ESS system here's what I think you should do. First, go out and buy a new main battery if your 2018 hasn't had one sooner. In this day and age of crappy AGM batteries, I'd replace mine every 3 years. Links are available on request for suitable substitutes.

Second, I want you to disconnect your smaller ESS/Aux battery, which itself is tucked away out of visibility, using the following method:

First, from the factory there are two black cables that lead to the main battery's negative post. One of those cables finds its other end at the passenger's front quarter panel. It is a body ground cable that you are to leave connected, untouched, as is.

The OTHER cable has as its distal end the negative terminal to the ESS/Aux battery. Disconnect it. Wrap its loose end in electric tape.

Next, closest to the front passenger's seat, under the hood, on top, is a black box known as your Power Distribution Center or PDC. Think of it as your vehicle's intelligent fuse box.

I want you to pop open its cover, locate Fuse 42, and pull that fuse out.

That should solve your problems if not explain the "why" aspect of things. Here's the why:

Your two batteries are connected in parallel (positive terminal to positive, negative to negative) at all times but an instant prior to crank, and during ESS events. Having those two batteries connected means one can cause the other's demise---and usually its the ESS/Aux battery that can negatively effect the main battery.

Pulling that cable I described takes the ESS/Aux battery out of the vehicle's electrical schematic.

But doing so can effect your ablity to crank**. That's where the Fuse 42 pull comes in. Pulling that fuse prevents the batteries from ever being separated in the 2 times I describe. All calls for power from either battery will now go to the main one.

Do turn off the ESS system with a button press or after market tech. We don't want ESS events running with that one main battery because it may rob the main/only battery of cranking power after the ESS event is over. That's what the ESS/Aux battery you just took out of the electrical circuit was for: i.e. to run appliances during an ESS event to preserve the main battery to handle the bulk of the post ESS event crank.

@@@@@@@@@@@@@

**later model 2018 JLs and all model years thereafter with dual AGM batteries will fail after disconnecting the ESS/Aux battery if Fuse 42*** is left in, but should crank on second attempt from the main battery. If successful, the vehicle will automatically take the ESS/Aux battery out of the vehicle's electrical schematic, crank thereafter on the first try and run off the main battery only, and put an ESS off light on in the dash forever more until the next cold crank, if any, where an energized ESS/Aux battery is detected.

The original 2018s though won't crank if the ESS/Aux battery is dead and Fuse 42 is left in. Not unless they have TSB 18-092-19 applied to them by the dealer, in which case they act like the aforementioned newer JLs.

I don't know which 2018 you have. If you have the later model ones or have TSB 18-092-19 you can just disconnect the ESS/Aux battery, attempt to crank, and if you fail, try again against the (new) main battery. This route will turn ESS off for you and run only against the main battery from that point until, as mentioned, an energized ESS/Aux battery is, if ever, reconnected.

But if you don't have TSB 18-092-19, or hate seeing an ESS off light in the dash, pull Fuse 42 and turn ESS off yourself.


@@@@@@@@@@@@

***Fuse 42 controls a relay that if energized, separates the two batteries. No fuse, no relay power. No replay power no separation of the battery cables.

I bought a used 2018, the ESS never worked on it. After doing all of the reading here I disconnected the cable and the car still started so I didn't worry about it. I replaced the main batter, and after installing the new battery it didn't start on the first push but started on the second push. I guess with the battery out it reset the memory and had to re-learn again. I had not heard about the fuse before for some reason, and I read everything here I could find. It has been 2 years since I did this and no problems with just the battery cable disconnected.

 

[Jeepsmashin]

For a while my ESS light was on, I just ignored it. My main battery died so I just replaced both batteries and now ESS works fine. And my jeep is also a 2018 JLUR

 

[txj2go]

For a while my ESS light was on, I just ignored it. My main battery died so I just replaced both batteries and now ESS works fine. And my jeep is also a 2018 JLUR

I didn't replace the small battery and never will, I prefer not to mess with ESS.

 

[PLR]

Thank you for your help and advice guys.

 

[Eischman]

For the past year my auto stop start does not work - not a problem as I don't like it and would normally switch it off - but...dealer said to charge the battery to full - I drove to Spain and back - 2000 miles - still not working - and sometimes the system powers down and switches off radio etc. Battery is nearly 4 years old - should I change it? - and I believe it has two batteries - why??
Thx,
Peter

Mine stopped working this past spring also, says battery is charging, even on 200-mile trips, it's a 2021 so batteries were only one year old??

 

[txj2go]

Mine stopped working this past spring also, says battery is charging, even on 200-mile trips, it's a 2021 so batteries were only one year old??

Apparently the OEM batteries can vary a lot in quality. When I removed the battery from my 3 year old 2018, the date stamp on the battery said it was 2 years old so the original battery had been replaced at 1 year.
Since I do trips to remote places I wanted the best battery I could find so I searched out and bought a battery with good reviews and reputation from the Batteries + store.

 

[Fudster]

I bought a used 2018, the ESS never worked on it. After doing all of the reading here I disconnected the cable and the car still started so I didn't worry about it. I replaced the main batter, and after installing the new battery it didn't start on the first push but started on the second push. I guess with the battery out it reset the memory and had to re-learn again. I had not heard about the fuse before for some reason, and I read everything here I could find. It has been 2 years since I did this and no problems with just the battery cable disconnected.

Here's what I think happened as a matter of explanation. I have to assume from what you are describing that your 2018 does indeed have TSB 18-092-19 --either because it was produced later into the 2018 year or the TSB was downloaded by a dealer.

Your "disconnecting the cable" I am interpreting to mean the removal of the black cable from the main battery's negative post whose other end leads to the negative post of the ESS/Aux battery: in so doing removing the ESS/Aux baterry from the electrical schematic of the vehicle.

Your 2018 did a pre-crank test of the ESS/Aux battery. It failed because it was disconnected. A subsequent crank attempt on your part, because of TSB 18-092-19 was attempted solely off the main battery.

It succeeded. The vehicle then proceeded to take the ESS/Aux battery out of the electrical schematic of the vehicle in ways that even if you reconnected that cable would still remain to be the case, throwing an ESS off light up on the dash, and cranking forever more on the first attempt from solely the main battery and running from it solely as well.

Your vehicle will remain in this state until the next crank where an energized ESS/Aux battery is reintroduced, if ever. If you don't mind the ESS off light in the dash I happen to think this method of running with one battery is better than the Fuse 42 pull or N1 to N2 jumper--not to disparage these approaches, because these latter two approaches require the owner to turn off ESS themselves.

I would say though that those who hate the ESS off light illumnated in the dash are better with these latter two techniques, and then turning ESS off with a button push or after market tech to do so.

 

[txj2go]

Here's what I think happened as a matter of explanation. I have to assume from what you are describing that your 2018 does indeed have TSB 18-092-19

All items correct.
I don't like the warning light in the dash display but I tolerate it because it is the lesser of the evils.

 

[bpb21]

I bought a used 2018, the ESS never worked on it. After doing all of the reading here I disconnected the cable and the car still started so I didn't worry about it. I replaced the main batter, and after installing the new battery it didn't start on the first push but started on the second push. I guess with the battery out it reset the memory and had to re-learn again. I had not heard about the fuse before for some reason, and I read everything here I could find. It has been 2 years since I did this and no problems with just the battery cable disconnected.

I'm close to the same; I bought a used 2018 and the ESS worked fine. Until it didn't. I did tons of reading on this forum and discovered the aux cable in question to the main battery was already disconnected. Also, that fuse (F42) had already been removed. Finally, I didn't take out the fuse box and panels to get to the aux battery but looking up from the bottom of the Jeep with a flashlight I'm fairly certain the aux battery had been removed (which would explain the fuse and cable being gone as well) as I could see where it would be and there looked to be a (factory made) hole where the aux battery would be housed (I could be way off on that detail, though).
Turns out one of the connectors to the main battery was lose/broken (or the screw that secures it, rather). I fixed that, tightened the rest, and all is well. I've got just one battery like normal and it's working great!

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