2019 Sahara Unlimited start/stop issue

[apolanco]

Anyone have an issue involving Start/Stop System problem? Six weeks ago, ignition start froze and acted as if the battery were dead. Immediately thereafter re-depressed start button and no problem with ignition. But on shutoff, same sequence repeated. Was diagnosed as a starter problem so replaced it with OEM starter. Today, the issue re-emerged. First start up is dead, but follow up Start/Stop function gets it started. Anyone experienced this??

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[Rhinebeck01]

Anyone have an issue involving Start/Stop System problem? Six weeks ago, ignition start froze and acted as if the battery were dead. Immediately thereafter re-depressed start button and no problem with ignition. But on shutoff, same sequence repeated. Was diagnosed as a starter problem so replaced it with OEM starter. Today, the issue re-emerged. First start up is dead, but follow up Start/Stop function gets it started. Anyone experienced this??

What you are seeing is the typical behavior for a dual battery system JL that has a depleted/bad/iffy auxiliary battery.

Starts on second ignition button push and you get an EVIC notice.

 

[Fudster]

Anyone have an issue involving Start/Stop System problem? Six weeks ago, ignition start froze and acted as if the battery were dead. Immediately thereafter re-depressed start button and no problem with ignition. But on shutoff, same sequence repeated. Was diagnosed as a starter problem so replaced it with OEM starter. Today, the issue re-emerged. First start up is dead, but follow up Start/Stop function gets it started. Anyone experienced this??

Yes. Before I comment on the "why's" and "what can be done's" about it, after this second Start/Stop function gets it started does an "ESS off" light appear in the dash?

While it's likely the ESS battery, the reason why a failing ESS battery can cause this, the suite of options you have available to you, and the things you should do beyond replacing or bypassing your ESS battery are topics you could benefit from knowing about.

But before I go down that road, you confirming for me the status of the ESS off light tells me I'm explaining a phenomenon that you're likely to be experiencing and not something else.

 

[apolanco]

Yes, an "ESS off" does appear on the dash after ignition. I attached three images. The first is the blank screen which appears immediately after the first attempt at ignition. During that period, I get an audio sound which sounds like the radio has been turned on and off in rapid succession. Maybe happens once or twice. Second image shows the ESS light after second attempt and actual igntion. Third image shows the Check Engine light illuminated.

 

[apolanco]

Here is the actual video. You can hear the "radio popping" approximately 2-3 seconds in.

 

[Fudster]

Hi again Arnold @apolanco :

While again, it sounds like your ESS battery is on its way out, understanding why its limited power is causing the things you're experiencing, the things you should do, and the options you have in response follows.

When your dual AGM battery JL is cold cranked it will seek to separate two batteries, which are normally connected in parallel at all times but this, and during ESS events, so as to test the ESS battery. If it passes this test both batteries are brought back into parallel to crank the engine.

If the test fails (and you're not running an early model 2018--which you're not), the crank will fail, but the next crank attempt will solely be against the main battery. If successful the vehicle will turn on the ESS off light in the dash, as ESS events, which are powered by the ESS battery alone are best not attempted given the limited power of the ESS battery.

If you're ESS battery is completely shot--and it sounds like yours has more power than this--future cold cranks will be against the main battery on the first try while this ESS off light remains lit. But it sounds like your ESS battery still has enough power in it for the vehicle to run its normal pre crank ESS battery test, but fail that test, and crank on the second attempt.

While replacing the ESS battery is certainly an option--and much has been written here how to do this yourself (links available on request), if you are not much a lover of the start stop features of the vehicle we can take the ESS battery out of the electrical schematic of the vehicle.

If this is desired, it's most easiest approach is to remove the black cable off of the main battery's negative post (there are 2) that does NOT have as its other cable end the body ground found on the passenger's front quarter panel under the hood. This cable that you are removing has as its other end the negative terminal of the ESS battery. Make sure to insulate the ends of this loose cable.

Now, a second step is normally taken to remove Fuse 42 from the vehicle's fuse box, a.k.a. the Power Distribution Center (PDC): the black box nearest the front passenger, but under the hood, on top. If you pull it's black cover off a map of the fuses should appear on the flip side of the cover.

Pulling Fuse 42 (please save the fuse) prevents the batteries from being isolated, so any calls to the ESS battery for power are directed to all batteries, of which there is only now one battery, the main one.

Given that it is advised to not run ESS events on only the main battery, I'd turn ESS off with that button in the dash or aftermarket tech (links available on request) to do so.

Finally, as a failing ESS battery can cannabilize the main battery, it might be a good idea to have the main battery load tested to see if it too needs replacement.

 

[apolanco]

Thanks so much for this wealth of information. While I routinely disable the ESS while operating (since I generally dislike it) I will probably go the aux battery replacement route rather than take it out of the schematic altogether. Again, thanks for the insight!

 

[Fudster]

Thanks so much for this wealth of information. While I routinely disable the ESS while operating (since I generally dislike it) I will probably go the aux battery replacement route rather than take it out of the schematic altogether. Again, thanks for the insight!

Often, when one of the two batteries dies it's time to change both, or at the very least have the surviving battery load tested in isolation.

This involves electrically separating the batteries and putting a load tester (not merely a volt tester) to the battery's terminals to test its ability to deliver and accept charge.

When batteries are in parallel it is best to pair identical size and type batteries. Someone "forgot to tell this" to Stellantis when they designed their ESS system's battery component. When batteries are in parallel, one its way out can rob the other of charge, particular in dissimilar size setups as these.

I'd hate for it to be the case that your ESS battery took your main out in a way that a charge can't restore it. It may also be, that if they are of similar age that it's time to replace both. But yet another worse scenario is your ESS took out your main, and putting a new ESS in has it taken out by your main.

 

[Fordaorm]

I had the same thing happen to my 2019 JLU. I currently have 72k miles and I have replaced the aux battery 2 times under warranty and once out of warranty. Now the battery is shot again. I just leave it disabled through the tazer.

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