Remote start/ aux battery.

[frankjc]

Hi. We have a 2018 JLU, 3.6. The start stop light is on. It does not function, even if we leave it on. Also, when the car sits over night, remote start does not work. It just clicks like a dead battery. It will work after the car has been driven. It starts fine when we start it using the start button in the car. If I recall correctly it does the same thing with both keys.
I've been googling, watching videos, etc, and it's getting confusing. Some people say replacing the aux battery fixed the remote start problem, but other people disconnect their aux battery. I'm gonna bust out the multimeter and check the voltage on the batteries after work.

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[Heimkehr]

What is the age of the batteries in the vehicle? Replacement might be indicated.

Know also that both batteries should be replaced at the same time, if you want to keep both in service.

 

[frankjc]

The batteries were in it when we bought it 1 year ago. There is a date in the main battery, but I don't remember what it is.

 

[AndySpill]

@frankjc Frank, here's the decision course I'd take.

It starts with a question. Do you want to run engine start stop events? I'm not judging: that's your decision.

If "no," I'm glad to link you with sources that can show you how to bypass the Aux battery. This action may too solve your remote start issue as well, but I'll save explanations on why until you write back indicating the course of action you wish to take.

And if you take this route I'd have the main battery load tested to see if it too needs replacement.

~~~~~

The other route is a desire to run ESS events, in which case I'd have both batteries independently load tested. As James @Heimkehr says, if either battery needs replacement I would replace both.

While this action may very well solve your issues there may be other factors at play aside from or in addition to your batteries that are causing your issues.

Finally, if main battery replacement is indicated I'd suggest that you acquire an H7 size battery. Depending on how our vehicle was original optioned from the factory, there may be a slightly smaller H6 battery installed, but an H7 will fit provided a cleat on the bottom of the battery tray is removed. I've found prices of both batteries comparable, so why not go with the slightly larger capacity one.

Indicate if you would like links to places on the forum where compatible brand batteries are sourced.

 

[frankjc]

The main driver of the JLU is my girlfriend. She doesn't like the start stop feature. Her main concern is having the remote start working.

 

[AndySpill]

The main driver of the JLU is my girlfriend. She doesn't like the start stop feature. Her main concern is having the remote start working.

Steps.

Locate two black factory cables at the main battery's negative post. One of those cables will have, at its distal end, the body ground connection on the passenger's front fender. Leave that cable connected and untouched.

The other factory cable at the main battery's negative post, sight unseen, has as its distal end the negative post of the Aux battery. It is that cable you should remove from the main battery's negative post, electric taping up its loose end and tucking it away.

Next, open the Power Distribution Center (PDC), the black box that contains the vehicle's fuses, typically near the main battery. Find Fuse 42. Remove it. Keep it somewhere safe.

Why the steps

If you don't desire ESS events that Aux battery connected is more trouble than it's worth. Your cable pull removes it from energizing vehicle appliances or getting charged. Sitting at the bottom of the engine bay behind the passenger's front tire, and as a sealed unit, it's very unlikely to leak, anymore than if it does, nothing stands between it and the ground. If you want to yank it I can link you instructions to do so, but it's optional.

Pulling Fuse 42 denies the Power Control Relay (PCR) from getting power. This is a normally closed relay that links the two batteries in parallel 99% of the time. The only time this relay gets energized, and in turn separates the batteries is for an instant when you cold crank, to test the Aux battery alone, and during ESS events.

Now, when you cold crank, unknown to the vehicle, the PCR doesn't get energized, so the cold crank test of the Aux battery goes against all connected batteries, of which you will only have one: your main battery. It's possible this battery will have ample power to pass this test, which may be turning your remote start off right now.

Please turn ESS off at the button on the dash, or buy tech to do this for you, links available upon request. I'd rather that you don't run ESS events with just one battery.

It may turn out that you also need a new main battery, but if you do, nothing about these steps was wasted time.

If this doesn't resolve your issues have your main battery load tested. If it needs replacement, as suggested, consider an H7 size replacement (you may already have an H7 in there.)

If all this doesn't solve your issues then no time or money was wasted. You took the Aux battery out of the equation, which is more trouble than its worth if you don't want to run ESS events, you replaced a dying main battery, and your situation will require further diagnosis by Stellantis.

It violates the rules of physics, if some Stellantis tech tells you, either out of ignorance or bad intent, that getting your remote start restored is a product of putting in a new Aux battery as well.

 

[BullMoose1776]

@frankjc Frank, here's the decision course I'd take.

It starts with a question. Do you want to run engine start stop events? I'm not judging: that's your decision.

If "no," I'm glad to link you with sources that can show you how to bypass the Aux battery. This action may too solve your remote start issue as well, but I'll save explanations on why until you write back indicating the course of action you wish to take.

And if you take this route I'd have the main battery load tested to see if it too needs replacement.

~~~~~

The other route is a desire to run ESS events, in which case I'd have both batteries independently load tested. As James @Heimkehr says, if either battery needs replacement I would replace both.

While this action may very well solve your issues there may be other factors at play aside from or in addition to your batteries that are causing your issues.

Finally, if main battery replacement is indicated I'd suggest that you acquire an H7 size battery. Depending on how our vehicle was original optioned from the factory, there may be a slightly smaller H6 battery installed, but an H7 will fit provided a cleat on the bottom of the battery tray is removed. I've found prices of both batteries comparable, so why not go with the slightly larger capacity one.

Indicate if you would like links to places on the forum where compatible brand batteries are sourced.

Load Testing of the batteries is the key statement here. AutoZone and others will test your battery, but that is not "Load Testing". I have a trusted mechanic who did it for me.

 

[alphawolff]

Hi. We have a 2018 JLU, 3.6. The start stop light is on. It does not function, even if we leave it on. Also, when the car sits over night, remote start does not work. It just clicks like a dead battery. It will work after the car has been driven. It starts fine when we start it using the start button in the car. If I recall correctly it does the same thing with both keys.
I've been googling, watching videos, etc, and it's getting confusing. Some people say replacing the aux battery fixed the remote start problem, but other people disconnect their aux battery. I'm gonna bust out the multimeter and check the voltage on the batteries after work.

Just replace both of your batteries. Don't over think this.

 

[frankjc]

Sounds good to me! Will the warning light still be on? I'm not sure if it matters to her, or how much.

 

[THAW]

Now that Fall is bringing colder weather, it's low battery season.

The JL has thresholds for CR[an]K (main) battery SoC to enable both ESS and Remote Start. The features are disabled because the battery isn't meeting the thresholds. After driving recharges the battery a bit, the thresholds may be met and the features re-enabled - sometimes only briefly.

If a charger is available, it might help. But, it's likely time to replace the battery/batteries.

 

[alphawolff]

Sounds good to me! Will the warning light still be on? I'm not sure if it matters to her, or how much.

You might need to clear the codes, but theyll clear on their own after awhile

 

[AndySpill]

A couple of thoughts here.

It's been my experience that what auto stores do provide is in fact load testing, which is what, if you are going to test your battery/ies you need, as opposed to a multimeter and its voltage readings.

While the low voltage of a multimeter can detect a failing battery, a battery with adequate voltage may still not be able to deliver power, and accept it back from the alternator well: something a load test better tests for and the true test of a battery.

I don't doubt a trusted mechanic knows how to do a proper load test. But I most definitely do not trust that mechanic (heck, I don't trust most Stellantis mechanics on this) to first take the cable I described above off the main battery's negative post before doing the load test. And without that step you will be load testing the two batteries as one composite battery, which can not only hide defects as the stronger of the two batteries compensates for the other's shortcomings, but fail to pinpoint which or both batteries require replacement.

I don't agree to simply replace both batteries for a bunch of reasons. First, we don't know their age or health. While their demise is the most likely culprit to your problems it's not guaranteed. Second, even if battery replacement is indicated, why replace both batteries if you have no desire to run ESS events? While it's entirely likely that battery replacement is indeed in your future, there's no reason to avoid tackling this problem in stages, spending money only as needed.

I'd start with the bypass. Then see if the ESS off light on the next crank shuts off. Then proceed on to load testing and if it fails, yes, go buy that new main battery.

As far as the warning lights are concerned @frankjc, the next cold crank after which the vehicle "sees" a healthy Aux battery should be the one in which the ESS off light in the dash turns off.

The operative word here is "sees." It comes in two forms. One involves replacing both batteries, and the other involves the bypass discussed, and a strong enough main battery: either the one you have or a replacement, as the Fuse 42 and cable pull of the bypass tricks the vehicle into seeing what it thinks is your Aux battery as what is in actuality your main battery.

 

[alphawolff]

A couple of thoughts here.

It's been my experience that what auto stores do provide is in fact load testing, which is what, if you are going to test your battery/ies you need, as opposed to a multimeter and its voltage readings.

While the low voltage of a multimeter can detect a failing battery, a battery with adequate voltage may still not be able to deliver power, and accept it back from the alternator well: something a load test better tests for and the true test of a battery.

I don't doubt a trusted mechanic knows how to do a proper load test. But I most definitely do not trust that mechanic (heck, I don't trust most Stellantis mechanics on this) to first take the cable I described above off the main battery's negative post before doing the load test. And without that step you will be load testing the two batteries as one composite battery, which can not only hide defects as the stronger of the two batteries compensates for the other's shortcomings, but fail to pinpoint which or both batteries require replacement.

I don't agree to simply replace both batteries for a bunch of reasons. First, we don't know their age or health. While their demise is the most likely culprit to your problems it's not guaranteed. Second, even if battery replacement is indicated, why replace both batteries if you have no desire to run ESS events? While it's entirely likely that battery replacement is indeed in your future, there's no reason to avoid tackling this problem in stages, spending money only as needed.

I'd start with the bypass. Then see if the ESS off light on the next crank shuts off. Then proceed on to load testing and if it fails, yes, go buy that new main battery.

As far as the warning lights are concerned @frankjc, the next cold crank after which the vehicle "sees" a healthy Aux battery should be the one in which the ESS off light in the dash turns off.

The operative word here is "sees." It comes in two forms. One involves replacing both batteries, and the other involves the bypass discussed, and a strong enough main battery: either the one you have or a replacement, as the Fuse 42 and cable pull of the bypass tricks the vehicle into seeing what it thinks is your Aux battery as what is in actuality your main battery.

Can confirm that most techs, even dealership techs, don't realize they need to disconnect the negative leads to isolate the batteries.

Honestly, under warranty if you have a battery issue I'm not testing shit, you're just getting new batteries. Stellantis pays us pennies to replace them, and pays us nothing to test them.

 

[Mguy]

So the conclusion here is that any time a stock alternator equipped JL has an ESS or remote start issue the off-warranty owner should just replace both batteries. No concern with battery age or use/charging history. Doesn't matter that the main battery might be in need of a full charge and aux disconnect, and then after an IBS reset the Jeep may run well with it for another two years. After all, everyone knows from the internet that Jeep AGM batteries, especially Mopars, are shit and just don't last.

 

[AndySpill]

So the conclusion here is that any time a stock alternator equipped JL has an ESS or remote start issue the off-warranty owner should just replace both batteries. No concern with battery age or use/charging history. Doesn't matter that the main battery might be in need of a full charge and aux disconnect, and then after an IBS reset the Jeep may run well with it for another two years. After all, everyone knows from the internet that Jeep AGM batteries, especially Mopars, are shit and just don't last.

@Mguy please let me add some nuance here.

Anytime that a, as you say stock alternator equipped JL, which I'll call a dual AGM battery JL, has an ESS or remote start issue, the off-warranty owner should ask themselves first, "do I want to run ESS events going forward from here?"

If the owner wants to run ESS events they may want to first try charging both batteries by hooking up a charger to the posts of the main battery. This will charge both batteries of a parked dual AGM battery JL. If they don't they can charge just the main battery by disconnecting the Aux battery consistent with steps below.

Next, if that owner wants to run ESS events they should disconnect the black cable on the negative post of the main battery that does NOT have as its distal end the body ground connection on the front passenger's panel.

Then, with a load tester, that person should place the positive lead of the load tester on the main battery's positive terminal (yes, I said main battery, that is not a typo) and the negative lead of the load tester on this loose cable. This action will solely load test the Aux battery.

Note the results.

If ESS is not desired going forward this load test step on the Aux battery can be skipped. We'll be bypassing the Aux battery, so its strength is moot.

Next, move the load tester's negative lead to the main battery's negative post. This will solely load test the main battery.

Note the results.

If both batteries test strong I would be inclined, once re-hooking up that cable to have a dealer take a look at why they are having problems.

If either battery is weak, and the owner wants to run ESS events I would suggest replacing both batteries, and recommend that the main battery be of type H7, even if the JL was equipped (it depends on options) with a slightly smaller H6. The H7 fits, but a cleat at the bottom of the battery tray will need to be removed first if the vehicle was equipped with the smaller H6.

I've found prices of both to be comparable, so why not have the beefier battery.

If the owner has no desire to run ESS events they should turn them off by pressing the button on the dash or acquire aftermarket tech to do this for them. They should then yank the cable discussed above permanently, electrical tapping its loose end, and pull Fuse 42 in the Power Distribution Center (PDC). If the main battery fails the load test it should be replaced as discussed above.

Certainly, if the battery/ies test well but are aged, the owner may wish to take this time to swap one of both as a preventative measure. I've been swapping my batteries every 3 years and I trickle charge them at rest, but that's just me.

And perhaps charging the battery/ies, particular younger ones, of a JL that's been sitting for quite some time might be enough, which is why I think hooking up a charger first might be best before load testing.

Links for further information on battery bypass, or battery suggestions are available on request.

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