ESS Warning Light (yea I know)

[MikeV1341]

So I have read many different threads and forums on this topic but there is so much conflicting info I just want to see people’s opinions on my situation.

2018 JLU Sahara
3.6
Auto

Bought this Jeep last week, first Jeep but not first 4wd Vehicle. The dealership during test drive told me the previous owner disabled ESS, which is fine with me as I always disable on my vehicles, my only issue is the ESS warning warning light on the dash. (A)!

After reading up on the Jeep ESS system I wanted to see how the previous owner “disabled” the ESS and I could not find anything. So I want ahead and isolated the battery and pulled fuse 42, I know this doesn’t disable ESS on its own, I would still need a tazer or one of those in/line disable alts for the switch. My question is, if the light is already on and the ESS wasn’t working to begin with since the previous owner “disabled” it, what would any of those products even do and would the light still be on anyway?

Am I just doomed to a dealer visit at this point?

thanks!

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[kah.mun.rah]

If the light is on the dash, it is possible that they just unplugged a hood plunger to disable it.

 

[MikeV1341]

If the light is on the dash, it is possible that they just unplugged a hood plunger to disable it.

Nope, both plungers are plugged in. Thanks though.

 

[AndySpill]

So I have read many different threads and forums on this topic but there is so much conflicting info I just want to see people’s opinions on my situation.

2018 JLU Sahara
3.6
Auto

Bought this Jeep last week, first Jeep but not first 4wd Vehicle. The dealership during test drive told me the previous owner disabled ESS, which is fine with me as I always disable on my vehicles, my only issue is the ESS warning warning light on the dash. (A)!

After reading up on the Jeep ESS system I wanted to see how the previous owner “disabled” the ESS and I could not find anything. So I want ahead and isolated the battery and pulled fuse 42, I know this doesn’t disable ESS on its own, I would still need a tazer or one of those in/line disable alts for the switch. My question is, if the light is already on and the ESS wasn’t working to begin with since the previous owner “disabled” it, what would any of those products even do and would the light still be on anyway?

Am I just doomed to a dealer visit at this point?

thanks!

Your not doomed. The most likely cause of your ESS light being on in the dash (that "A" symbol with a circle a slash indicating the vehicle (as opposed to you or aftermarket tech) has turned ESS off), given the way you described your setup (this doesn't apply to everyone), is a main battery in need of replacement.

At cold crank the factory procedure is to energize the Power Control Relay (PCR), care of an intact Fuse 42, to separate the batteries and test their power. An inadequately powered ESS/Aux battery revealed during such a test can then cause that light to turn on.

With your bypass implemented that test still occurs, only, care of your Fuse 42 removal, the PCR can't be energized to separate the batteries, and the vehicle, unknown to its own diagnostics, runs the aforementioned test against all connected batteries, of which in your case you only have one: your main.

This is why the situation you describe, for JLs with bypassed Aux batteries, often implicates the main battery.

I suggest you have that battery load tested: in other words attached to a meter that doesn't merely test its voltage (i.e. like a multimeter can) but one which applies a resistive load to see how the battery respond to being taxed (i.e. being asked to do "that which a battery should do, delivery power.") Many auto stores will loan you a load tester.

~~~~~~~~~~

Probably not realizing it you've raised a point that's come up on the forum before that goes something like this: Why don't I disconnect the Aux battery but leave Fuse 42 intact? The cold crank test won't find any Aux battery, it will turn the ESS light on in the dash and I won't need to press the ESS off button or spend money on tech to turn ESS off for me.

Yes, in that case, to answer your question, said tech (or pushing the ESS off button at cold crank) would provide no additional ESS feature. But instead, I think you should aim to get the ESS off light turned off in the dash and turn it off yourself by hand or tech. I say this because the person on this forum who invented this technique @Jebiruph held the view that the ESS off light is a bit of the (I'm paraphrasing him) proverbial Canary in a Coal Mine (a device detecting issues) whose illumination can signify issues that can be masked if the light is always on.

~~~~~~~~~~~

P.S. If you need a new battery I suggest you buy one of the H7, not the slightly smaller H6 variety, even if your vehicle was equipped with an H6.

Stellantis options the larger battery with the beefier alternator option but your JL can accomodate the larger H7 provided a cleat is removed in the bottom of the main battery compartment. For pretty much the same price why not get a beefier battery? I've had good luck with Odyssey brand ones but there are other brands people like as well.

https://www.jlwranglerforums.com/forum/threads/main-battery-replacement-talk-jl-jt.100534/

 

[Jebiruph]

Is the IBS plugged in? Otherwise they may have removed the aux battery.

 

[mishkajb]

I have a 21 JLU. I have the Tazer installed. I can push the ASS button 20 times, it doesn't change anything. My thought is the switch is still energized so pushing it still illuminates it. It doesn't change anything, ASS still is disabled.

I also have the ASS unavailable/service now error, going to unplug the Tazer, restart the Jeep and let it communicate at OEM settings and see if that clears the code. If not, I'll be taking it to the Jeep dealership to see if the aux system has an issue, or the aux battery is going bad.

Sidenote - I bought mine used at a Chevy/GMC dealership. They could not work on it, their equipment can't interface with that system. So it's off to the actual DJC dealership.

 

[AndySpill]

I have a 21 JLU. I have the Tazer installed. I can push the ASS button 20 times, it doesn't change anything. My thought is the switch is still energized so pushing it still illuminates it. It doesn't change anything, ASS still is disabled.

I also have the ASS unavailable/service now error, going to unplug the Tazer, restart the Jeep and let it communicate at OEM settings and see if that clears the code. If not, I'll be taking it to the Jeep dealership to see if the aux system has an issue, or the aux battery is going bad.

Sidenote - I bought mine used at a Chevy/GMC dealership. They could not work on it, their equipment can't interface with that system. So it's off to the actual DJC dealership.

I like to characterize ESS not working into 3 categories.

The first is you turning it off at the bottom or with tech to do so.

The second is some condition not being met that can be seen in dash messages, like the engine being to cold, or ESS not ready for some other reason, maybe too low battery voltages.

And the third and more potentially problematic one that turns the ESS off light (the "A" with the near circle around it and the slash thru it) on in the dash which that (often?) arises from pre-crank diagnostic checks.

 

[mishkajb]

Yes, that is what my code is, after the diagnostic check. It's about 3 seconds after startup when it pops up. It's already disabled, so I'm not losing sleep over it right now!

 

[mwilk012]

Yes, that is what my code is, after the diagnostic check. It's about 3 seconds after startup when it pops up. It's already disabled, so I'm not losing sleep over it right now!

What code? No DTC’s have been mentioned here.

 

[mishkajb]

"Automatic Start/Stop System Unavailable"
"Service Auto Start/Stop System"

 

[mwilk012]

"Automatic Start/Stop System Unavailable"
"Service Auto Start/Stop System"

Those are not codes. They are generic warning messages. You need to retrieve the actual DTC’s in order to more accurately diagnose.

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