Start/Stop Problem

[Jebiruph]

I just bought my first Wrangler in July. 2018 JL Sahara. The Start/Stop function wasn’t working but I read that if the A/C was on it didn’t work so I really worried about it. A few days ago it was finally cool enough to not run the A/C and turn Start/Stop Stop still wasn’t working. I scrolled through the menu and saw the message Battery Charging. Even after driving it Start/Stop wasn’t working. I thought I had a 3 month 3,000 mile warranty so I took it in. I was told the sensor was bad and that the sensor and both batteries need to be replaced. $868.88! AND it was not covered by the warranty. (That was only for the power train they said) UGH!

Can I have the Start/Stop disabled completely and just replace the mail battery? Any info on this would be helpful.

Since you don't know the history of the batteries, you don't know if the batteries are original or not. Get the batteries charged up and have them individually load tested. Replace the main battery if it fails the load test. If the aux fails, you can replace it or just disconnect it. The battery sensor doesn't control charging voltage, so it can't over charge them.

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[Jammalynn]

If the batteries are original to your 2018 Jeep, it's entirely possible that they're reaching the end of their practical service life. The dodginess of the Start/Stop function may simply be a manifestation of their age. Aging batteries can cause any number of seemingly unrelated electric issues/problems (voice of experience here.) Do consider replacing both of them as a prophylactic measure. Possibly the "sensor" that they claim is a problem...isn't. New batteries should make plain whether or not it's faulty.

Yes, that battery replacement wasn't done prior the sale, by a dealership who should arguably know better, is a mild annoyance.

I am a school teacher. $868.88 is more than a mild annoyance for me. That is a big hit on my budget.

 

[Fudster]

The answer to the OPs question is simple. Replace both the Main and Aux batteries. That's it.

@Reinen: your solution, and it's a good one for most owners, including me, I fear, is neither the answer to the OPs question nor ideal for him.

His question, at least as I see it, was "Can I have the Start/Stop disabled completely and just replace the mail (main) battery?"

1. ESS is a canary in the coal mine for battery issues. It's nearly always the first thing to go when batteries start going bad but it isn't essential. Don't ignore it. It's just a matter of time before some other essential electrical component starts failing strangely and you could very well be stranded.

True, and invariably, as you must know it's that dang Aux battery that's the "canary" you describe, although in a 2018, both batteries. yes, ****normally (not for the OP) need to be replaced. The steps below though, specific for the OP and others like him make only the main battery replacement necessary.

As I see it, replacing both batteries for a guy who wants to run with one battery and wants (or is willing) to turn ESS off is not ideal. You'll be making him spend money on something (and aux battery) he neither wants nor needs and whose presence makes things potentially more problematic for someone who isn't going to use ESS.

I absolutely agree with you though that the main battery should be replaced no matter what.

Ignore what the dealer said about the sensor. It's very likely they sold you a Jeep with practically dead batteries and are finding a scapegoat to blame, adding a sensor to your bill to do it. That should tell you all you need to know about them. If it's a 2018 with original batteries, they've already lasted longer than average.

Speaking in general terms I do concur with you that a 2018 is overdue for one or both batteries being replaced. But for this fellow a a) main battery replaced, a b) fuse pulled as per my linked instructions, an c) aux battery disconnected, and an d) ESS disengaged (though the method of his choosing) is more his ticket, if not the only way for him to run with one battery and ESS off. A second way is detailed below.

I believe that this method should not cause the ESS off light in the dash to occur. ESS though will not be turned off for him automatically.

1. l always replace both Main and Aux batteries at the same time.

Again if the OP wanted to run two batteries (or ESS, which should be done on a dual battery JL with both batteries) I'd agree that your way of doing things should be his way.

Again, I did exactly what you did.

But it's not what I think the OP wants. His desire to run with only the main battery, as long as he is willing to disconnect the Aux battery, so it can have no negative impact on the main battery, and turn off ESS, makes the Aux's purchase a waste of money for him IMHO.

1. The batteries are always linked, except during starts. If you do not replace both, the one that wasn't replaced will severely shorten the lifespan of the new battery.

The batteries in a dual battery JL are in parallel but for an instant at cold crank and ESS events.

There's exceptions to that too.

To point: if you're not running a later model 2018 or later, and/or don't have TSB 18-092-19 , a dead aux battery JL will strand the vehicle. But, if you do, upon second cold crank attempt, seconds later, the vehicle will automatically disconnect the aux battery and try cranking with the main battery only. (Normally, both batteries energize the crank.)

This fact can be used as an alternative method for the OP to achieve his one battery ESS off objective, provided he has TSB 18-092-19 or its functionality, because if he disconnects the Aux battery as described, so it is seen by the vehicle as "dead" and his main battery (yes, a new one) cranks, an ESS off light gets put up in the dash, and ESS will be ***forever turned off. In addition to his cable removal isolating the ESS battery, (say for example this battery was connected but dead,) the vehicle would automatically isolate it ***forever as well.

***Not until/if the aux battery is replaced and he reattaches that cable, that Aux battery is taken out of the electrical circuit. Unlike the prior method no fuse is pulled and you get an idiot light on the dash, but you also get ESS turned off for you with no other steps.

It's all about whether you can tolerate the idiot light on the dash. If you can't, or don't have TSB 18-092-19 or its functionality, choose method 1, and turn off ESS with a button push at crank or with tech. If you can tolerate the idiot light, method two may be cheaper/easier.

This first method is reversible by backing out its steps.

The second is reversible once/if a charged ESS battery is reconnected and a cold crank is attempted. That next cold crank after a charged and connected ESS battery is seen should restore the vehicle to its normal cranking logic where the ESS battery is isolated for an instant at crank for testing, and if shown to have power, both batteries are put into parallel to crank the engine, and remain in parallel until the next cold crank or ESS event.

...just trying to save the OP $ on something he neither wants (ESS battery) nor needs nor wishes to spend on, and that is a "canary in the mine" potential source of problems, as you say, for those willing to not run ESS....should that motorcycle battery go bad and start cannibalizing the main battery.

BTW, not only am I NOT an expert, but what little I know I owe to Jerry @Jebiruph, who chimed in above.....he discovered and published all these finding on the forum!

 

[Jammalynn]

Your query I suspect occupies more discussion on the forum than any other single topic.

You ask two distinct questions. Restated, you could a) prevent Start Stop from engaging, or b) run with one or two batteries, or c) both. Not that its recommended or what you want but you could even d) run Start Stop with one battery.

On the one hand I don't want this answer to be as long as "War and Peace." On the other hand I don't know what I can assume you already know.

Still more, the earlier 2018 3.6L (like you may have) JLs won't crank without either an auxiliary battery with ample power (which could be too little power to engage ESS,) or its cables rerouted to the main battery, or TSB 18-092-19 installed from the dealer. At cold crank the Aux battery is normally isolated for a second from the main battery, which it is connected to it in parallel with the factory wiring at all times but this instant and during ESS events.

If you have one of these older 2018s and bought your vehicle from the dealer, I would hope that they applied this TSB before the sold you the vehicle, but it may not be required like bringing all recalls up to date before putting the vehicle in your hands.

That's a lot to digest for a newbie, but nonetheless the facts.

Since the introduction of your model year, forum members have come up with 2 primary ways to get around this battery isolation and keep both batteries in parallel at all times. The initial method involved jumpering two connections in the PDC (Power Distribution Center), and the current easier method involves pulling a fuse in the PDC https://www.jlwranglerforums.com/forum/threads/jumperless-aux-battery-bypass.95945/

The PDC is that black box under the hood, on top, closest to the front passenger's seat. It's your vehicle's fuse box with logic encoded within it.

Using either method I describe above prevents the auxiliary battery from being isolated, channeling all requests for power from it to both batteries. This also means that once you've done either method, if you want, you (the dealer won't do this for you) can take the Auxiliary battery completely out of the electrical system of the vehicle if you want, the easiest way to do so being to disconnect the black cable from this battery that attaches to the negative pole of the main battery.

At the negative pole of the main battery expect to see two black cables. The other end of one of those cables leads to the body ground on the front passenger's quarter panel. Leave that alone. It's the other cable you disconnect, wrapping its end it electric tape.

Again--don't do this before the jumper or fuse technique above is effected if you have an old 2018 3.6 without TSB 18-092-19. (I can only imagine how my words must sound to the inexperienced!!!)

Now for the second part of your question, turning off ESS....

Your going to want to do this if you run just one battery even if you loved rather than hated ESS.

This is because engaging ESS with the one main battery is robbing that battery of cranking power after the ESS event. Normally, appliances run solely off the Auxiliary battery during an ESS event to preserve this cranking power. Sure, other vehicles run ESS with one battery but the dual battery JLs aren't designed for this.

There must be over 1/2 dozen ways to disable ESS, and I'll put the techniques in 3 categories.

The first is pushing the ESS off button after every crank. The second are DIY techniques for insuring ESS doesn't engage, like disconnecting (or better, turning sideways https://www.jlwranglerforums.com/forum/threads/free-ess-disable-via-hood-pin.15350/) the hood open sensor closest to the driver's seat, or with TSB 18-092-19 installed or a later model 2018 or later, pulling that black cable, and attempting to crank the vehicle twice. The second attempt will move all power to the main battery, and like disconnecting the hood sensor discussed throw an error light in the display (EVIC) turning ESS off.

Some people don't like the idiot lights. And some of these DIYs come with side effects. For example, I think disconnecting (not turning sideways) the hood sensor disables remote engine start functionality.

The 3rd category of ways to turn off ESS is through the purchase of tech to do so. From the Smart Start/Stop module, to the Z Automotive Tazer JL, and other toys, that allow you to program ESS to always be off. The former is cheaper and just does an ESS shutoff; the latter more expensive with many additional features.

That's already too much for 1 post.

Thank you for sharing all the information. I definitely have a lot to learn. I have a friend who can work on my Jeep for me. I will have him read your post for me and dumb it down for my level of understanding. Plus he would be the one to make any alterations for me. Again, I really appreciate all the info!!! Thank you.

 

[Fudster]

Since you don't know the history of the batteries, you don't know if the batteries are original or not. Get the batteries charged up and have them individually load tested. Replace the main battery if it fails the load test. If the aux fails, you can replace it or just disconnect it. The battery sensor doesn't control charging voltage, so it can't over charge them.

It's an excellent point Jerry. I'm assuming, perhaps incorrectly, that the batteries are original equipment.

 

[Fudster]

Thank you for sharing all the information. I definitely have a lot to learn. I have a friend who can work on my Jeep for me. I will have him read your post for me and dumb it down for my level of understanding. Plus he would be the one to make any alterations for me. Again, I really appreciate all the info!!! Thank you.

Ask questions like a 3 year old with no fear of judgement.

We all had the knowledge of a 3 year old about JLs at one point.

 

[Jammalynn]

Since you don't know the history of the batteries, you don't know if the batteries are original or not. Get the batteries charged up and have them individually load tested. Replace the main battery if it fails the load test. If the aux fails, you can replace it or just disconnect it. The battery sensor doesn't control charging voltage, so it can't over charge them.

He told me the over charting situation was a very rare occurrence. I am beginning to think it is so rare that it isn’t even the problem, based on the replies here. I think they are taking advantage of my lack of experience and knowledge. Thank you for the information.

 

[Fudster]

He told me the over charting situation was a very rare occurrence. I am beginning to think it is so rare that it isn’t even the problem, based on the replies here. I think they are taking advantage of my lack of experience and knowledge. Thank you for the information.

Jerry is absolutely correct I think about your first step.

I suspect that your going to find one or both batteries in need of replacement, and even if you don't, if those batteries are original to your 2018 they're due, at least the main one as per my instructions, for replacement.

Here's how you load test each battery independently. If you can gain access to a load tester (many Auto stores will loan you one) do not simply place it on the main battery's leads. That would load test both batteries together. You don't want that.

A load tester is NOT a voltage tester. It's a device that puts electrical resistance on the line to test the battery's ability to deliver charge, not merely, like a voltage tester, note instantaneous (voltage) charge.

Rather, disconnect the black cable from the ESS battery to the main battery's negative as I describe above and set that cable aside, away from metal.

Now put the load tester's prongs on the main battery. Viola, you're load testing only the main battery. Record your findings.

With that done move the load tester's negative side only to the dangling cable. Now your testing the ESS battery.

Yeah, I know the load tester's positive is still on the main battery. I stand by what I said: your testing the ESS battery now.

Reconnect that cable and report your findings.

 

[Jammalynn]

@Reinen: your solution, and it's a good one for most owners, including me, I fear, is neither the answer to the OPs question nor ideal for him.

His question, at least as I see it, was "Can I have the Start/Stop disabled completely and just replace the mail (main) battery?"



True, and invariably, as you must know it's that dang Aux battery that's the "canary" you describe, although in a 2018, both batteries. yes, ****normally (not for the OP) need to be replaced. The steps below though, specific for the OP and others like him make only the main battery replacement necessary.

As I see it, replacing both batteries for a guy who wants to run with one battery and wants (or is willing) to turn ESS off is not ideal. You'll be making him spend money on something (and aux battery) he neither wants nor needs and whose presence makes things potentially more problematic for someone who isn't going to use ESS.

I absolutely agree with you though that the main battery should be replaced no matter what.



Speaking in general terms I do concur with you that a 2018 is overdue for one or both batteries being replaced. But for this fellow a a) main battery replaced, a b) fuse pulled as per my linked instructions, an c) aux battery disconnected, and an d) ESS disengaged (though the method of his choosing) is more his ticket, if not the only way for him to run with one battery and ESS off. A second way is detailed below.

I believe that this method should not cause the ESS off light in the dash to occur. ESS though will not be turned off for him automatically.



Again if the OP wanted to run two batteries (or ESS, which should be done on a dual battery JL with both batteries) I'd agree that your way of doing things should be his way.

Again, I did exactly what you did.

But it's not what I think the OP wants. His desire to run with only the main battery, as long as he is willing to disconnect the Aux battery, so it can have no negative impact on the main battery, and turn off ESS, makes the Aux's purchase a waste of money for him IMHO.



The batteries in a dual battery JL are in parallel but for an instant at cold crank and ESS events.

There's exceptions to that too.

To point: if you're not running a later model 2018 or later, and/or don't have TSB 18-092-19 , a dead aux battery JL will strand the vehicle. But, if you do, upon second cold crank attempt, seconds later, the vehicle will automatically disconnect the aux battery and try cranking with the main battery only. (Normally, both batteries energize the crank.)

This fact can be used as an alternative method for the OP to achieve his one battery ESS off objective, provided he has TSB 18-092-19 or its functionality, because if he disconnects the Aux battery as described, so it is seen by the vehicle as "dead" and his main battery (yes, a new one) cranks, an ESS off light gets put up in the dash, and ESS will be ***forever turned off. In addition to his cable removal isolating the ESS battery, (say for example this battery was connected but dead,) the vehicle would automatically isolate it ***forever as well.

***Not until/if the aux battery is replaced and he reattaches that cable, that Aux battery is taken out of the electrical circuit. Unlike the prior method no fuse is pulled and you get an idiot light on the dash, but you also get ESS turned off for you with no other steps.

It's all about whether you can tolerate the idiot light on the dash. If you can't, or don't have TSB 18-092-19 or its functionality, choose method 1, and turn off ESS with a button push at crank or with tech. If you can tolerate the idiot light, method two may be cheaper/easier.

This first method is reversible by backing out its steps.

The second is reversible once/if a charged ESS battery is reconnected and a cold crank is attempted. That next cold crank after a charged and connected ESS battery is seen should restore the vehicle to its normal cranking logic where the ESS battery is isolated for an instant at crank for testing, and if shown to have power, both batteries are put into parallel to crank the engine, and remain in parallel until the next cold crank or ESS event.

...just trying to save the OP $ on something he neither wants (ESS battery) nor needs nor wishes to spend on, and that is a "canary in the mine" potential source of problems, as you say, for those willing to not run ESS....should that motorcycle battery go bad and start cannibalizing the main battery.

BTW, not only am I NOT an expert, but what little I know I owe to Jerry @Jebiruph, who chimed in above.....he discovered and published all these finding on the forum!

I was totally struck by the cost of replacing the sensor and both batteries. Since my original post I have calmed down some. With your information I do feel like I can make a much more informed decision about what to do. I will probably suck it up and pay the bill. It is just a lot to pay after only having my Jeep for less than two months. Plus I really think this problem has been going on since day one but I just wasn’t informed enough to know to look for it. I thought the ESS just never kicked in because I was always running the A/C. I guess you live and learn…. This was an expensive lesson for me.

 

[rhocking]

Since you don't know the history of the batteries, you don't know if the batteries are original or not. Get the batteries charged up and have them individually load tested. Replace the main battery if it fails the load test. If the aux fails, you can replace it or just disconnect it. The battery sensor doesn't control charging voltage, so it can't over charge them.

This is the best answer so far (as usual from Jebiruph who is widely considered the expert on all things battery).

To expand on this a bit.

If you find that the both the main battery and the aux battery are bad I suspect that the reason your stop/start does not work has nothing to do with the sensor. Many people have reported stop/start not working because the batteries were bad. FYI I personally had this ESS issue but fortunately for me it was fixed under warranty by replacing both batteries.

If both batteries are bad AND you do not care for the ESS functionality my recommendation is to replace just the main battery with an H7 battery. The H7 is slightly more expensive than an H6 but the extra cost is well worth it. See this thread
https://www.jlwranglerforums.com/forum/threads/??-main-battery-replacement-talk-jl-jt.100534/#post-2082809

Then disconnect the bad Aux battery and run with just a main:
This as simple as removing fuse 42 and disconnecting a wire. See this thread
https://www.jlwranglerforums.com/forum/threads/jumperless-aux-battery-bypass.95945/

It depends on your need but I believe running just the main will be your best (not quite cheapest because of the H7 rated battery) solution.

The downside to this solution is that with a single battery you now need to avoid using ESS. Every time you start you will have to disable ESS. FYI ESS will still work but with a single battery it is not a good idea to use it.

PS If disabling the ESS every time is something you want to avoid or becomes too much of a pain you can automatically disable ESS with either a SmartStopStart (the owner is a long time forum contributor) or a Tazer (more functions but more expensive).

 

[TaiMc]

They told me the sensor and both batteries have to be replaced. My question is, Do I have to replace the sensor and auxiliary battery if I don’t want to use Start/Stop?

The Auxiliary battery is used for more than just the Auto Start/Stop. It powers other technology in the Jeep.

I had an issue with mine and it prevented me from cranking it. I then figured out a way to bypass the system to have it crank (turned the jeep "on" and then pressed the auto start/stop disable button, then cranked). However, this was only a quick fix so that I could get the jeep running. I eventually had to replace the battery myself as other functions of the Jeep started to act crazy with random notifications (a non-mopar Jeep specialist told me that it would do this).

I would not recommend paying that price to have the battery changed. Replacing the aux battery is not a problem to do (it's really simple once you remove the front passenger fender).

However, I'm not sure about these sensors, where they are located and how difficult it is to replace them. I'm sure other members will chime in and advise you on whether or not it is a job you can do yourself. It sux that they sold you a Jeep that they knew had flaws or knew would eventually have flaws. We all know that the batteries are an issue with these rigs.

 

[TaiMc]

They gave you a load of crap. Over charging is highly, highly unlikely.

lol...I've never heard of "overcharging before". They should've just replaced the batteries and see if that fixed the issue. lol @ these "sensors" being faulty....

 

[Bill_P]

He told me the over charting situation was a very rare occurrence. I am beginning to think it is so rare that it isn’t even the problem, based on the replies here. I think they are taking advantage of my lack of experience and knowledge. Thank you for the information.

It is extremely rare. In fact, it only happens when they have sold a car with bad batteries to someone and they want to make that someone pay extra for the dealership error.

 

[Jebiruph]

I was totally struck by the cost of replacing the sensor and both batteries. Since my original post I have calmed down some. With your information I do feel like I can make a much more informed decision about what to do. I will probably suck it up and pay the bill. It is just a lot to pay after only having my Jeep for less than two months. Plus I really think this problem has been going on since day one but I just wasn’t informed enough to know to look for it. I thought the ESS just never kicked in because I was always running the A/C. I guess you live and learn…. This was an expensive lesson for me.

There is a trade off between how much you are able/willing to do yourself and how much you are able/willing to pay for. A good compromise is to skip the charging/testing of the main battery and buy a new one from an auto parts store. They will install it for free and it should cost around $250.

Everyone will say you have to replace both batteries at the same time, but you don't. My main battery failed at 2.5 years and my aux battery still tested good at 3.5 years. It wouldn't be a bad idea to disconnect the aux battery which involves disconnecting a battery cable and pulling a fuse.

If you have access to an electrical outlet near where you park at night, it's a good idea to occasionally put a charger on the batteries anyway, so buying a charger first to charge and test the batteries might not be a bad place to start.

Whatever you do, don't pay for a new battery sensor, they almost never go bad.

 

[Htfan]

They told me that the sensor overcharged both batteries. I plan to get something to disable this feature. Any suggestions?

The dealer service manager who told you that gets a "Red Flag" I would NOT trust them! If the batteries are the original from the factory, they are simply warn out and should have been replaced by the dealer before it was sold 2 months ago.

As far as disabling the feature, many on this forum use one of the Tazer products. However, I have not tried it myself.

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