AUX battery?

[alparmer]

I have been experiencing the AUX Lights not available which goes off after a few minutes. Today, on the dash, a red A! and the A has almost a complete circle. I think that is the start/stop. My first guess is the aux battery causing these faults? Only 27k on this 2022.

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[Flip]

My first guess is the aux battery causing these faults?

Yes, I agree. Disconnect the auxiliary ground, pull F42 fuse. You should be good.

 

[AndySpill]

Hey Al, @Flip is likely right (that is if you own a JL Wrangler with dual AGM batteries) , if not complete.

On the negative post of the main battery do you see two factory cables or one? The presence of two would indicate that you likely have a dual AGM battery JL, where that Aux battery resides, sight unseen, under some other under the hood components, not the least of which being the PDC, or Power Distribution Center, a.k.a. your intelligent fuse box.

It is likely that one or both of your batteries are in need of replacement, and whether you replace one of both should best be guided by whether those batteries are 1) in need of replacement, and 2) whether you want to run ESS events.

If I were you I'd temporarily disconnect the cable @Flip speaks of, if it exists in your JL, (it is the thinner of the two cables, leave the other one attached) and then load test the main battery. You may be able to borrow a load tester from an auto parts store.

That cable disconnect insures that your test is solely of the main battery, not both batteries together--again *if* you have a dual AGM battery JL.

If that battery 1) shows need of replacement, and 2) you have no desire to run ESS events, and 3) have a dual AGM JL, I'd suggest you do the bypass @Flip suggests (detailed instructions available on request), and turn ESS off at the console button or with tech to do it for you automatically. I'd also recommend that you replace the main battery with a group H7 size battery, even if, depending upon how you optioned your vehicle, it was equipped with a slightly smaller H6. Both batteries will fit in a JL (you'll need to remove a cleat in the bottom of the battery tray to fit an H7 if you were equipped with an H6.)

Given their comparable prices, why not go with the slightly larger battery?

You don't need to do the bypass if your JL is equipped with just one AGM battery. For example the Etorque has a second battery, but it is a propulsion battery of different chemistry and voltage than your 12V battery.

If you 1) want to run ESS events, 2) have dual AGM batteries, and 3) your main battery tests strongly, I would normally suggest that you move that load tester's negative lead to the removed cable, as it will, even as its positive side remains on the main battery, solely test the Aux battery. But this is moot, here's why.

If 1) that main battery is in need of replacement and 2) you want to run ESS events and have a 3) dual AGM battery JL you'd be wise to replace the Aux battery as well, even if the Aux battery were to have tested strong.

If the 1)main battery tested strong and 2)you want to run ESS events and 3) have a dual AGM battery JL, then test the Aux battery. If it is weak, again, you will be advised to replace both batteries.

Put that cable back on, or do the bypass, and buy the battery/ies you need.

Links on replacement main and Aux batteries are available on request.

If all batteries load tested strong I'd suggest you take the vehicle to a dealer for service.

 

[58Willys]

Load test both batteries separately to to figure out the issue.

 

[SoK66]

We have five '21 JT Max Tows in tour service. One at a time I've been disabling the AUX battery (pulling the small neg cable at the battery, zip tying it out of the way and insulating the terminal , yanking the #42 fuse). Not a single issue to date.

 

[wolfdog]

2018 JLU main battery lasted 5 years, then disconnect six went One year more when main Original battery quit, pretty good!!!

main battery does ESS starting, aux useless! Have been using main new battery for over a year now rarely use ESS shut off button! Usually dodge ESSbyslow stopping!

Had a 2015 Cherokee Trailhawk with ESS and one battery that worked fine til traded in 2023! Aux batteries are useless! If you disconnect Aux only thing wearing out is your starter!!

Go Jeep!!!

 

[Ryanh]

at a time I've been disabling the AUX battery (pulling the small neg cable at the battery, zip tying it out of t

I did the same thing for a couple years, but the light was driving me crazy. So I paid almost $400 just for a light to go away.

 

[SoK66]

I did the same thing for a couple years, but the light was driving me crazy. So I paid almost $400 just for a light to go away.

The light has always gone out when I do the delete. I should have mentioned that I have installed new main batteries at the same time as disabling the AUX and yanking the 42 fuse.

 

[Ryanh]

The light has always gone out when I do the delete. I should have mentioned that I have installed new main batteries at the same time as disabling the AUX and yanking the 42 fuse.

Ah! Well, good to know for next time.

 

[alparmer]

Thanks to all that replied. I've attached a couple of pics of the battery terminals. You can clearly see corrosion on the Pos side. I think I may have to replace both batteries. From the looks of it, it appears the Aux delete is the way to go. I have the Tazer so the ESS is disabled.

 

[alparmer]

My first guess is the aux battery causing these faults?

Yes, I agree. Disconnect the auxiliary ground, pull F42 fuse. You should be good.

I disconnected the aux batt ground from the main batt and pulled fuse 42. Now I have no aux lights since the aux batt is disco and still have the dash A! Light on.

Hey Al, @Flip is likely right (that is if you own a JL Wrangler with dual AGM batteries) , if not complete.

On the negative post of the main battery do you see two factory cables or one? The presence of two would indicate that you likely have a dual AGM battery JL, where that Aux battery resides, sight unseen, under some other under the hood components, not the least of which being the PDC, or Power Distribution Center, a.k.a. your intelligent fuse box.

It is likely that one or both of your batteries are in need of replacement, and whether you replace one of both should best be guided by whether those batteries are 1) in need of replacement, and 2) whether you want to run ESS events.

If I were you I'd temporarily disconnect the cable @Flip speaks of, if it exists in your JL, (it is the thinner of the two cables, leave the other one attached) and then load test the main battery. You may be able to borrow a load tester from an auto parts store.

That cable disconnect insures that your test is solely of the main battery, not both batteries together--again *if* you have a dual AGM battery JL.

If that battery 1) shows need of replacement, and 2) you have no desire to run ESS events, and 3) have a dual AGM JL, I'd suggest you do the bypass @Flip suggests (detailed instructions available on request), and turn ESS off at the console button or with tech to do it for you automatically. I'd also recommend that you replace the main battery with a group H7 size battery, even if, depending upon how you optioned your vehicle, it was equipped with a slightly smaller H6. Both batteries will fit in a JL (you'll need to remove a cleat in the bottom of the battery tray to fit an H7 if you were equipped with an H6.)

Given their comparable prices, why not go with the slightly larger battery?

You don't need to do the bypass if your JL is equipped with just one AGM battery. For example the Etorque has a second battery, but it is a propulsion battery of different chemistry and voltage than your 12V battery.

If you 1) want to run ESS events, 2) have dual AGM batteries, and 3) your main battery tests strongly, I would normally suggest that you move that load tester's negative lead to the removed cable, as it will, even as its positive side remains on the main battery, solely test the Aux battery. But this is moot, here's why.

If 1) that main battery is in need of replacement and 2) you want to run ESS events and have a 3) dual AGM battery JL you'd be wise to replace the Aux battery as well, even if the Aux battery were to have tested strong.

If the 1)main battery tested strong and 2)you want to run ESS events and 3) have a dual AGM battery JL, then test the Aux battery. If it is weak, again, you will be advised to replace both batteries.

Put that cable back on, or do the bypass, and buy the battery/ies you need.

Links on replacement main and Aux batteries are available on request.

If all batteries load tested strong I'd suggest you take the vehicle to a dealer for service.

I disconnected the aux batt ground from the main batt. I also pulled fuse 42. Same A! error on the dash and now I don't have my aux lights, which is no big deal. However I cannot clear the A! dash error. I'm guessing it could be the main battery. The dash shows the voltage at 14.1 but thats coming from the alternator. At rest it is 12v, can't find my load tester, but that seems low to me. This is a leas and will turn it in this August. Not sure what the cheapest way to fix this, but don't want to turn it in with that dash error. I'm sure they'll make me pay for both batteries. TIA

 

[SoK66]

The "A!" warning light is for the main battery. You can try a charger on it overnight and see if it goes out, BUT be sure to not attach the ground clamp from the charger to the negative battery terminal. Attach it to the unpainted stud located where the ground cables attach to the body. In that way the current from the charger will go through the IBS (Intelligent Battery Sensor), which will than in turn know the main battery true volytage and state of charge.

 

[THAW]

Thanks to all that replied. I've attached a couple of pics of the battery terminals. You can clearly see corrosion on the Pos side. I think I may have to replace both batteries. From the looks of it, it appears the Aux delete is the way to go. I have the Tazer so the ESS is disabled.

Your main battery is leaking. Replace it immediately, and make sure the acid didn't spread to other parts.

 

[AndySpill]

I disconnected the aux batt ground from the main batt and pulled fuse 42. Now I have no aux lights since the aux batt is disco and still have the dash A! Light on.

I disconnected the aux batt ground from the main batt. I also pulled fuse 42. Same A! error on the dash and now I don't have my aux lights, which is no big deal. However I cannot clear the A! dash error. I'm guessing it could be the main battery. The dash shows the voltage at 14.1 but thats coming from the alternator. At rest it is 12v, can't find my load tester, but that seems low to me. This is a leas and will turn it in this August. Not sure what the cheapest way to fix this, but don't want to turn it in with that dash error. I'm sure they'll make me pay for both batteries. TIA

The dual AGM battery JL will, upon cold crank, enable the ESS off light in the dash (the "A" with the slash icon) if the Aux battery, which it tests upon start up, **or what the vehicle thinks** is the Aux battery is lacking power.

Your disconnecting of both the Aux battery and Fuse 42 silently redirects this Aux battery test to the main battery, which the vehicle thinks the aforementioned test happen on the Aux battery.

I'd load test the main battery and replace it with a group H7 as I described if it has aged out. It's not hard to do this swap yourself, or have a non-Stellantis tech do for you, who won't insist on the two battery configuration. If you have a slightly smaller H6 battery there now, you will need to remove a cleat in the bottom of the main battery tray to accommodate the slightly larger H7 battery.

This is the point where @THAW usually gets his geek on and says that bypassing the Aux and Fuse 42 is not a silent change to the vehicle as it only allows for six ESS events with each cold crank of the engine.

This is true provided you don't turn ESS off at the dash button (or via aftermarket tech to do so) which I always recommend when running just a main battery on a dual AGM battery JL.

 

[THAW]

I'd load test the main battery...

Bad advice. Do not load test a leaking battery.

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