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How to: Disconnect AUX battery and run just off the main with no errors! PICS!

54835 Views 111 Replies 28 Participants Last post by  cbrenthus
EDIT: I want to be clear that this does not disable ESS. Simply disconnecting the AUX battery will disable ESS, but that will throw an error. Doing the following has no affect on ESS, it will continue to work as normal, just off the main battery :). If you want to disable ESS, that is a different subject.

ANOTHER EDIT: Please seat your fuses- open your fuse block and simply press down on every fuse, you'll be surprised how many click into place. This has been reported to solve many gremlins, and the 90 seconds it takes is worth ruling it out ;)

I have both a wrangler and pacifica running the same dual battery system with ESS. I don't like ESS and disable it every time, and installed a smart start stop on the pacifica so its always disabled. I also really don't like the dual battery setup - I understand the idea behind it but the engineers really messed up when they decided to leave the batteries in parallel when the engine is off, thus a bad battery takes them both down. I also wonder if the AUX batteries get overcharged due to being charged as long as the main is being charged, thus causing them to fail prematurely.

So, a quick overview of the dual battery system on your pacfica: The main battery is used for starting the engine, and the aux battery is used for running the electronics when the ESS shuts off the engine during a stop. By doing so, it preserves your main battery to start the engine back up, something that's pretty important when in traffic. The part that separates the batteries is the Power Control Relay (PCR). When you press the start button, the computer sends a signal to the PCR to separate the batteries, and then checks the voltage to ensure that the AUX battery has voltage to power everything during an ESS stop. This AUX voltage check takes 1/10 of a second or less, so you don't notice it, but if the computer doesn't get full voltage, it disables ESS and you get an error message. This is why simply disconnecting the AUX battery doesn't really work - you'll get an error message every time you start. If this doesn't bother you, than go for it and it will also disable ESS (I ran my wrangler like this for a few months). Although, if you go this route, and wish to reconnect the AUX, you will need to disconnect both batteries for a few minutes first to erase the error, or use a code reader to clear it.

So, to not receive the error, you need to disconnect the PCR. What we are doing here is removing the signal wire that tells the PCR to separate the batteries. Now, when the computer tells the PCR to separate the batteries, the PCR doesn't get the message, leaves both batteries connected, and that is the voltage the computer reads. With the PCR unplugged and the AUX disconnected, the computer is reading the voltage from the main battery when it thinks it is reading from the AUX.

Now that you understand how the system works and what we are doing to bypass it, lets get started:

Open the hood and remove the airbox connector to service the batteries. To remove the airbox, refer to the picture below for the screw / bolts needed (each one is circled in yellow). The airbox cover might be 8MM and not 10MM, I can't remember. The PCR that needs to be unplugged is circled in red. If you have small hands or a really talented you might be able to unplug the PCR without removing the airbox, but it only takes a few minutes and gives you much more room.
44531



Now that everything is removed, you can easily access the PCR. You want to unplug the signal wire shown below. To do so you need to pop the gray tab out, then squeeze the connector as you pull it off. DO NOT FORCE IT!!! You don't want to break this. It can be a bit difficult, but not overly so. See below, and while I think the posts I labeled as "don't touch" are negatives so it should be fine, its best not to touch them anyway. EDIT: I was reviewing a wiring diagram and it looks like these are actually positive, so absolutely don't touch them (or disconnect both batteries before doing this procedure, which is a good idea anyway). I'm not impressed that FCA didn't make these red and/or cover them.

44532


Now all you have to do is disconnect the negative from the AUX battery, wrap it in electrical tape to be safe, and you are done. I zip tied mine down to keep it out of the way.

44533


Then put the airbox back together and you are good to go, running on a single battery the way it should be ;) Just remember to put it all back if you go to the dealer for anything!
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EDIT: I want to be clear that this does not disable ESS. Simply disconnecting the AUX battery will disable ESS, but that will throw an error. Doing the following has no affect on ESS, it will continue to work as normal, just off the main battery :). If you want to disable ESS, that is a different subject.

ANOTHER EDIT: Please seat your fuses- open your fuse block and simply press down on every fuse, you'll be surprised how many click into place. This has been reported to solve many gremlins, and the 90 seconds it takes is worth ruling it out ;)

I have both a wrangler and pacifica running the same dual battery system with ESS. I don't like ESS and disable it every time, and installed a smart start stop on the pacifica so its always disabled. I also really don't like the dual battery setup - I understand the idea behind it but the engineers really messed up when they decided to leave the batteries in parallel when the engine is off, thus a bad battery takes them both down. I also wonder if the AUX batteries get overcharged due to being charged as long as the main is being charged, thus causing them to fail prematurely.

So, a quick overview of the dual battery system on your pacfica: The main battery is used for starting the engine, and the aux battery is used for running the electronics when the ESS shuts off the engine during a stop. By doing so, it preserves your main battery to start the engine back up, something that's pretty important when in traffic. The part that separates the batteries is the Power Control Relay (PCR). When you press the start button, the computer sends a signal to the PCR to separate the batteries, and then checks the voltage to ensure that the AUX battery has voltage to power everything during an ESS stop. This AUX voltage check takes 1/10 of a second or less, so you don't notice it, but if the computer doesn't get full voltage, it disables ESS and you get an error message. This is why simply disconnecting the AUX battery doesn't really work - you'll get an error message every time you start. If this doesn't bother you, than go for it and it will also disable ESS (I ran my wrangler like this for a few months). Although, if you go this route, and wish to reconnect the AUX, you will need to disconnect both batteries for a few minutes first to erase the error, or use a code reader to clear it.

So, to not receive the error, you need to disconnect the PCR. What we are doing here is removing the signal wire that tells the PCR to separate the batteries. Now, when the computer tells the PCR to separate the batteries, the PCR doesn't get the message, leaves both batteries connected, and that is the voltage the computer reads. With the PCR unplugged and the AUX disconnected, the computer is reading the voltage from the main battery when it thinks it is reading from the AUX.

Now that you understand how the system works and what we are doing to bypass it, lets get started:

Open the hood and remove the airbox connector to service the batteries. To remove the airbox, refer to the picture below for the screw / bolts needed (each one is circled in yellow). The airbox cover might be 8MM and not 10MM, I can't remember. The PCR that needs to be unplugged is circled in red. If you have small hands or a really talented you might be able to unplug the PCR without removing the airbox, but it only takes a few minutes and gives you much more room.
View attachment 44531


Now that everything is removed, you can easily access the PCR. You want to unplug the signal wire shown below. To do so you need to pop the gray tab out, then squeeze the connector as you pull it off. DO NOT FORCE IT!!! You don't want to break this. It can be a bit difficult, but not overly so. See below, and while I think the posts I labeled as "don't touch" are negatives so it should be fine, its best not to touch them anyway. EDIT: I was reviewing a wiring diagram and it looks like these are actually positive, so absolutely don't touch them (or disconnect both batteries before doing this procedure, which is a good idea anyway). I'm not impressed that FCA didn't make these red and/or cover them.

View attachment 44532

Now all you have to do is disconnect the negative from the AUX battery, wrap it in electrical tape to be safe, and you are done. I zip tied mine down to keep it out of the way.

View attachment 44533

Then put the airbox back together and you are good to go, running on a single battery the way it should be ;) Just remember to put it all back if you go to the dealer for anything!
Obviously a great presentation and this procedure can definitely be considered but the Auto Stop Eliminator $89 which I purchased 2 years ago and installed should be strongly recommended also in lieu of this, it keeps the ESS position memory you last left it so you never have to push the button again.. Pushed the button once 2 years ago My ESS has been off ever since no dash lights, no issues and is a perfect godsend.. With the ESS battery never being used again and constantly being charged by the alternator the smaller battery should last 2 to 3 years and it's just a $99 quick replacement at Autozone as an Aux14 battery to keep the system whole and factory like new. Even mildly butchering a new expensive van like this would just bug me because something's been taken apart and something you really shouldn't do to a new vehicle because you're still virtually running off the main most of the time now anyway in both scenarios just my opinion..... Not to mention most of these Vans are still under warranty if you have to head to the dealer for any reason you have to redo everything again back to factory...
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I know yours was an older post, tried to do it today but could not remove the plastic box directly under the filter, there is a small nut at the bottom but when I turn it ccw it seems to get tighter and the box did not come off for that reason. I did remove the aux battery and replaced the main, but I get an error on the display saying download failed error number 20, this leaves the display on and I think eventualy runs down the battery (s).
Not sure why you weren't able to remove the lower airbox, but best not to keep turning the nut if it isn't working. And are you saying that you are running without the AUX battery without doing this procedure? That will cause an error, but I don't think he error you are experiencing.

Obviously a great presentation and this procedure can definitely be considered but the Auto Stop Eliminator $89 which I purchased 2 years ago and installed should be strongly recommended also in lieu of this, it keeps the ESS position memory you last left it so you never have to push the button again.. Pushed the button once 2 years ago My ESS has been off ever since no dash lights, no issues and is a perfect godsend.. With the ESS battery never being used again and constantly being charged by the alternator the smaller battery should last 2 to 3 years and it's just a $99 quick replacement at Autozone as an Aux14 battery to keep the system whole and factory like new. Even mildly butchering a new expensive van like this would just bug me because something's been taken apart and something you really shouldn't do to a new vehicle because you're still virtually running off the main most of the time now anyway in both scenarios just my opinion..... Not to mention most of these Vans are still under warranty if you have to head to the dealer for any reason you have to redo everything again back to factory...
I have the Smart Auto Start Stop as well, and many people have found that if you don't use the ESS (and thus put the AUX battery through its paces) the AUX battery fails even quicker. There is no scientific proof of this, but over on the JL forums there were many reports of AUX's failing in less than a year. And when the AUX goes, it will almost certainly take your main with it unless you miraculously catch it in time. And this is not butchering the vehicle, trust me, I've done mods that involve cutting wires and such on new vehicles over the years, but this can be taken back to stock in 10 minutes and the dealer wouldn't even know it was modded ;)

But, it's your vehicle and if you don't like it, don't do it. ;)
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Not sure why you weren't able to remove the lower airbox, but best not to keep turning the nut if it isn't working. And are you saying that you are running without the AUX battery without doing this procedure? That will cause an error, but I don't think he error you are experiencing.



I have the Smart Auto Start Stop as well, and many people have found that if you don't use the ESS (and thus put the AUX battery through its paces) the AUX battery fails even quicker. There is no scientific proof of this, but over on the JL forums there were many reports of AUX's failing in less than a year. And when the AUX goes, it will almost certainly take your main with it unless you miraculously catch it in time. And this is not butchering the vehicle, trust me, I've done mods that involve cutting wires and such on new vehicles over the years, but this can be taken back to stock in 10 minutes and the dealer wouldn't even know it was modded ;)

But, it's your vehicle and if you don't like it, don't do it. ;)
I just have experience with the Aux battery that lasted about 3 years and never used the ESS once in that time. The yellow circle light did come on and I even waited a week to replace it and the main battery was still fully charged it wasn't a big deal.. People are so worried that if the aux battery goes out it's going to immediately take down the big battery with it and actually that would take a lot of time because your alternator is still charging the main constantly. If you simply change out the aux battery in a reasonable amount of time when you get the warning light you'll always be okay.
I think butchering was a strong word that's why I said mildly and should have said something different but even doing aftermarket stuff like that on a nice new van it's just something I probably wouldn't do I just don't think it's that necessary, I would just keep it whole with the Auto Stop start installed and just replace the aux battery once every 3 years but who knows what the future holds. Nonetheless good job馃憤
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Not sure why you weren't able to remove the lower airbox, but best not to keep turning the nut if it isn't working. And are you saying that you are running without the AUX battery without doing this procedure? That will cause an error, but I don't think he error you are experiencing.



I have the Smart Auto Start Stop as well, and many people have found that if you don't use the ESS (and thus put the AUX battery through its paces) the AUX battery fails even quicker. There is no scientific proof of this, but over on the JL forums there were many reports of AUX's failing in less than a year. And when the AUX goes, it will almost certainly take your main with it unless you miraculously catch it in time. And this is not butchering the vehicle, trust me, I've done mods that involve cutting wires and such on new vehicles over the years, but this can be taken back to stock in 10 minutes and the dealer wouldn't even know it was modded ;)

But, it's your vehicle and if you don't like it, don't do it. ;)
Yes Aux battery removed, I was having a uconnect update error, I think this was my original problem without knowing it, it was failing and I thought I would let it sit and see if it would finish. When I next looked at the car the batteries were dead. I want to remove the cable as you showed but my fat hands can get near enough. I tried to use hemostats but not sure how the tab comes out perpendicular or parallel to the cable. I really would like to remove the black plastic filter box but not sure what the design is, did your nut come straight out off the thread ccw?
I do have the aux error. I have removed the F76 fuse to stop the cycle of my uconnect failing and running the battery down. Now the car is operating as it should, turning off when I turn it off.

If I can get that plug off as your procedure shows I will live without the aux battery and the uconnect since I think it is a terrible design. The uconnect should never take priority over the car transportation. I use the car first for transportation and it must always work within reason.

I hope my gibberish is clear.
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EDIT: I want to be clear that this does not disable ESS. Simply disconnecting the AUX battery will disable ESS, but that will throw an error. Doing the following has no affect on ESS, it will continue to work as normal, just off the main battery :). If you want to disable ESS, that is a different subject.

ANOTHER EDIT: Please seat your fuses- open your fuse block and simply press down on every fuse, you'll be surprised how many click into place. This has been reported to solve many gremlins, and the 90 seconds it takes is worth ruling it out ;)

I have both a wrangler and pacifica running the same dual battery system with ESS. I don't like ESS and disable it every time, and installed a smart start stop on the pacifica so its always disabled. I also really don't like the dual battery setup - I understand the idea behind it but the engineers really messed up when they decided to leave the batteries in parallel when the engine is off, thus a bad battery takes them both down. I also wonder if the AUX batteries get overcharged due to being charged as long as the main is being charged, thus causing them to fail prematurely.

So, a quick overview of the dual battery system on your pacfica: The main battery is used for starting the engine, and the aux battery is used for running the electronics when the ESS shuts off the engine during a stop. By doing so, it preserves your main battery to start the engine back up, something that's pretty important when in traffic. The part that separates the batteries is the Power Control Relay (PCR). When you press the start button, the computer sends a signal to the PCR to separate the batteries, and then checks the voltage to ensure that the AUX battery has voltage to power everything during an ESS stop. This AUX voltage check takes 1/10 of a second or less, so you don't notice it, but if the computer doesn't get full voltage, it disables ESS and you get an error message. This is why simply disconnecting the AUX battery doesn't really work - you'll get an error message every time you start. If this doesn't bother you, than go for it and it will also disable ESS (I ran my wrangler like this for a few months). Although, if you go this route, and wish to reconnect the AUX, you will need to disconnect both batteries for a few minutes first to erase the error, or use a code reader to clear it.

So, to not receive the error, you need to disconnect the PCR. What we are doing here is removing the signal wire that tells the PCR to separate the batteries. Now, when the computer tells the PCR to separate the batteries, the PCR doesn't get the message, leaves both batteries connected, and that is the voltage the computer reads. With the PCR unplugged and the AUX disconnected, the computer is reading the voltage from the main battery when it thinks it is reading from the AUX.

Now that you understand how the system works and what we are doing to bypass it, lets get started:

Open the hood and remove the airbox connector to service the batteries. To remove the airbox, refer to the picture below for the screw / bolts needed (each one is circled in yellow). The airbox cover might be 8MM and not 10MM, I can't remember. The PCR that needs to be unplugged is circled in red. If you have small hands or a really talented you might be able to unplug the PCR without removing the airbox, but it only takes a few minutes and gives you much more room.
View attachment 44531


Now that everything is removed, you can easily access the PCR. You want to unplug the signal wire shown below. To do so you need to pop the gray tab out, then squeeze the connector as you pull it off. DO NOT FORCE IT!!! You don't want to break this. It can be a bit difficult, but not overly so. See below, and while I think the posts I labeled as "don't touch" are negatives so it should be fine, its best not to touch them anyway. EDIT: I was reviewing a wiring diagram and it looks like these are actually positive, so absolutely don't touch them (or disconnect both batteries before doing this procedure, which is a good idea anyway). I'm not impressed that FCA didn't make these red and/or cover them.

View attachment 44532

Now all you have to do is disconnect the negative from the AUX battery, wrap it in electrical tape to be safe, and you are done. I zip tied mine down to keep it out of the way.

View attachment 44533

Then put the airbox back together and you are good to go, running on a single battery the way it should be ;) Just remember to put it all back if you go to the dealer for anything!
Hello,
I wanted to say thank you for this post. I disconnected the Aux battery and the PCR and so far the main battery has not drained which was happening before...

The only strange thing is the ESS A circle light went away but the car never does the auto stop start anymore. I am not sure why since you mentioned it should still function but it does not bother me. I purchased an auto stop eliminator device to be sure the feature would not begin functioning in the future as a precaution and leave me stranded but I was curious why the ESS did not function again just with the solution provided here... Maybe I need to disconnect the main battery to reset since I was getting the A with Circle error prior to this...

Anyways. Thank you! This seems to work for me and I lost alot of money with the dealership who changed a perfectly working alternator and batteries to never resolve the issue...
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If you don't have the @ light, but start stop isn't working, scroll through the menu until you get to the start stop status. Most likely it will say "battery charging". This just means the IBS (intelligent battery sensor) isn't seeing enough of a charge to activate ESS, but there isn't anything specifically wrong. My JLUR was like this for 3 years, starting 6 months after I got it until 11/10/22 when it sat outside overnight on a cold night and wouldn't start (and a few hours after spending $250 on a new battery I got the call that my Bronco arrived at the dealer!).

Anyways, a few times over the years after driving a long distance the ESS would work again in the Jeep for a few days. And the ESS started working after I put in the new battery. Oh, and my remote start stopped working last winter and I knew it was because the battery was a bit low and meant to change it before the cold this year. So if your main is going, you'll see signs.
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Hello,
I wanted to say thank you for this post. I disconnected the Aux battery and the PCR and so far the main battery has not drained which was happening before...

The only strange thing is the ESS A circle light went away but the car never does the auto stop start anymore. I am not sure why since you mentioned it should still function but it does not bother me. I purchased an auto stop eliminator device to be sure the feature would not begin functioning in the future as a precaution and leave me stranded but I was curious why the ESS did not function again just with the solution provided here... Maybe I need to disconnect the main battery to reset since I was getting the A with Circle error prior to this...

Anyways. Thank you! This seems to work for me and I lost alot of money with the dealership who changed a perfectly working alternator and batteries to never resolve the issue...
Can you tell me how you were able to remove the black plastic housing for the air filter? Mine has a post inside facing up with a small nut. Did you remove this nut or is there something I am missing?

thanks
We did that 2 weeks ago after someone mentioned it to me at the Chrysler dealer ( shhhh!!)
Yes it works.
I might have missed it but do you still get a light on the dash after unplugging the neg cable on the six battery?
I might have missed it but do you still get a light on the dash after unplugging the neg cable on the six battery?
Yes you'll get the yellow circle light and then it Chimes when it turns on and then it will read a message warning saying stop starting not available. It's not worth looking at all that keeping that negative terminal disconnected it feels like you're driving a broken car everyday
I think I am gonna go with the auto stop Eliminator. They have one available for 2018 to 2022. I don't know what happens if I do go this route if the aux battery dies? I am also going to inquire at the dealer incognito and ask if it will cause a warranty issue. No biggie it is only a5 minute process to add or remove it, maybe 10
I think I am gonna go with the auto stop Eliminator. They have one available for 2018 to 2022. I don't know what happens if I do go this route if the aux battery dies? I am also going to inquire at the dealer incognito and ask if it will cause a warranty issue. No biggie it is only a5 minute process to add or remove it, maybe 10
I have the '18 TL also and it's the best thing you'll ever do. It'll take about 15 minutes to install you just pop out the black shifter plate and it's a three-prong module you just tie into a few things watch the Youtube video it's fairly easy.18 through 21 or 22 is the same, the '17 is different with an easier plug in module under the steering wheel.. it won't void any warranty they'll never know it's there just don't say anything.. I installed it two years ago I've never hit the ESS button once since, I hate it... The smaller Aux battery is only used when at a stop when the engine is off to run your lights air conditioning and electrical until the engine starts again so never using ESS will prolong the life of that battery.. The main batt under every circumstance restarts the car again.
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I have a limited and the Smart Start Stop installed behind the passenger sliding door. I love it as well. As for the Aux battery, the consensus awhile back on the Wrangler forum was that not using ESS actually made the Aux fail quicker as it was designed to be used ;)
I have a limited and the Smart Start Stop installed behind the passenger sliding door. I love it as well. As for the Aux battery, the consensus awhile back on the Wrangler forum was that not using ESS actually made the Aux fail quicker as it was designed to be used ;)
Hmmm I think I'm gonna go against the grain on that, even if you never use ESS the alternator is always charging both batteries so Not using ESS at all the battery should always last longer verses using it, I could argue its common sense....IMO
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Hmmm I think I'm gonna go against the grain on that, even if you never use ESS the alternator is always charging both batteries so Not using ESS at all the battery should always last longer verses using it, I could argue its common sense....IMO
We can go back on forth on this all day, but on the JL forums a while back most people that were having AUX battery failures were not using ESS. Constantly charging a battery without ever using it is not a good thing. These vehicles do have IBS, but that means that when the main is used to start the vehicle, it will charge for a while which in turn charges the AUX, even though the AUX is already at full charge, which is not good. This is why battery tenders exist ;)
EDIT: I want to be clear that this does not disable ESS. Simply disconnecting the AUX battery will disable ESS, but that will throw an error. Doing the following has no affect on ESS, it will continue to work as normal, just off the main battery :). If you want to disable ESS, that is a different subject. ANOTHER EDIT: Please seat your fuses- open your fuse block and simply press down on every fuse, you'll be surprised how many click into place. This has been reported to solve many gremlins, and the 90 seconds it takes is worth ruling it out ;) I have both a wrangler and pacifica running the same dual battery system with ESS. I don't like ESS and disable it every time, and installed a smart start stop on the pacifica so its always disabled. I also really don't like the dual battery setup - I understand the idea behind it but the engineers really messed up when they decided to leave the batteries in parallel when the engine is off, thus a bad battery takes them both down. I also wonder if the AUX batteries get overcharged due to being charged as long as the main is being charged, thus causing them to fail prematurely. So, a quick overview of the dual battery system on your pacfica: The main battery is used for starting the engine, and the aux battery is used for running the electronics when the ESS shuts off the engine during a stop. By doing so, it preserves your main battery to start the engine back up, something that's pretty important when in traffic. The part that separates the batteries is the Power Control Relay (PCR). When you press the start button, the computer sends a signal to the PCR to separate the batteries, and then checks the voltage to ensure that the AUX battery has voltage to power everything during an ESS stop. This AUX voltage check takes 1/10 of a second or less, so you don't notice it, but if the computer doesn't get full voltage, it disables ESS and you get an error message. This is why simply disconnecting the AUX battery doesn't really work - you'll get an error message every time you start. If this doesn't bother you, than go for it and it will also disable ESS (I ran my wrangler like this for a few months). Although, if you go this route, and wish to reconnect the AUX, you will need to disconnect both batteries for a few minutes first to erase the error, or use a code reader to clear it. So, to not receive the error, you need to disconnect the PCR. What we are doing here is removing the signal wire that tells the PCR to separate the batteries. Now, when the computer tells the PCR to separate the batteries, the PCR doesn't get the message, leaves both batteries connected, and that is the voltage the computer reads. With the PCR unplugged and the AUX disconnected, the computer is reading the voltage from the main battery when it thinks it is reading from the AUX. Now that you understand how the system works and what we are doing to bypass it, lets get started: Open the hood and remove the airbox connector to service the batteries. To remove the airbox, refer to the picture below for the screw / bolts needed (each one is circled in yellow). The airbox cover might be 8MM and not 10MM, I can't remember. The PCR that needs to be unplugged is circled in red. If you have small hands or a really talented you might be able to unplug the PCR without removing the airbox, but it only takes a few minutes and gives you much more room. View attachment 44531 Now that everything is removed, you can easily access the PCR. You want to unplug the signal wire shown below. To do so you need to pop the gray tab out, then squeeze the connector as you pull it off. DO NOT FORCE IT!!! You don't want to break this. It can be a bit difficult, but not overly so. See below, and while I think the posts I labeled as "don't touch" are negatives so it should be fine, its best not to touch them anyway. EDIT: I was reviewing a wiring diagram and it looks like these are actually positive, so absolutely don't touch them (or disconnect both batteries before doing this procedure, which is a good idea anyway). I'm not impressed that FCA didn't make these red and/or cover them. View attachment 44532 Now all you have to do is disconnect the negative from the AUX battery, wrap it in electrical tape to be safe, and you are done. I zip tied mine down to keep it out of the way. View attachment 44533 Then put the airbox back together and you are good to go, running on a single battery the way it should be ;) Just remember to put it all back if you go to the dealer for anything!
This is helping me tremendously! Followed all youre steps and just taped off the neg wire. Should I still hook up the positive on the AUX battery? Thanks.
EDIT: I want to be clear that this does not disable ESS. Simply disconnecting the AUX battery will disable ESS, but that will throw an error. Doing the following has no affect on ESS, it will continue to work as normal, just off the main battery :). If you want to disable ESS, that is a different subject.

ANOTHER EDIT: Please seat your fuses- open your fuse block and simply press down on every fuse, you'll be surprised how many click into place. This has been reported to solve many gremlins, and the 90 seconds it takes is worth ruling it out ;)

I have both a wrangler and pacifica running the same dual battery system with ESS. I don't like ESS and disable it every time, and installed a smart start stop on the pacifica so its always disabled. I also really don't like the dual battery setup - I understand the idea behind it but the engineers really messed up when they decided to leave the batteries in parallel when the engine is off, thus a bad battery takes them both down. I also wonder if the AUX batteries get overcharged due to being charged as long as the main is being charged, thus causing them to fail prematurely.

So, a quick overview of the dual battery system on your pacfica: The main battery is used for starting the engine, and the aux battery is used for running the electronics when the ESS shuts off the engine during a stop. By doing so, it preserves your main battery to start the engine back up, something that's pretty important when in traffic. The part that separates the batteries is the Power Control Relay (PCR). When you press the start button, the computer sends a signal to the PCR to separate the batteries, and then checks the voltage to ensure that the AUX battery has voltage to power everything during an ESS stop. This AUX voltage check takes 1/10 of a second or less, so you don't notice it, but if the computer doesn't get full voltage, it disables ESS and you get an error message. This is why simply disconnecting the AUX battery doesn't really work - you'll get an error message every time you start. If this doesn't bother you, than go for it and it will also disable ESS (I ran my wrangler like this for a few months). Although, if you go this route, and wish to reconnect the AUX, you will need to disconnect both batteries for a few minutes first to erase the error, or use a code reader to clear it.

So, to not receive the error, you need to disconnect the PCR. What we are doing here is removing the signal wire that tells the PCR to separate the batteries. Now, when the computer tells the PCR to separate the batteries, the PCR doesn't get the message, leaves both batteries connected, and that is the voltage the computer reads. With the PCR unplugged and the AUX disconnected, the computer is reading the voltage from the main battery when it thinks it is reading from the AUX.

Now that you understand how the system works and what we are doing to bypass it, lets get started:

Open the hood and remove the airbox connector to service the batteries. To remove the airbox, refer to the picture below for the screw / bolts needed (each one is circled in yellow). The airbox cover might be 8MM and not 10MM, I can't remember. The PCR that needs to be unplugged is circled in red. If you have small hands or a really talented you might be able to unplug the PCR without removing the airbox, but it only takes a few minutes and gives you much more room.
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Now that everything is removed, you can easily access the PCR. You want to unplug the signal wire shown below. To do so you need to pop the gray tab out, then squeeze the connector as you pull it off. DO NOT FORCE IT!!! You don't want to break this. It can be a bit difficult, but not overly so. See below, and while I think the posts I labeled as "don't touch" are negatives so it should be fine, its best not to touch them anyway. EDIT: I was reviewing a wiring diagram and it looks like these are actually positive, so absolutely don't touch them (or disconnect both batteries before doing this procedure, which is a good idea anyway). I'm not impressed that FCA didn't make these red and/or cover them.

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Now all you have to do is disconnect the negative from the AUX battery, wrap it in electrical tape to be safe, and you are done. I zip tied mine down to keep it out of the way.

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Then put the airbox back together and you are good to go, running on a single battery the way it should be ;) Just remember to put it all back if you go to the dealer for anything!
thank you for this post! It helped tremendously! I just finished writing up my negative wire in taping. Should I still connect the positive back to AUX battery? Thanks.
If you removed the positive from the AUX, you can leave it. I never disconnected the positive from the AUX, but disconnecting the negative simply disconnects the AUX.
If you do disconnect the positive cable, be sure you tape it up so it cannot come in contact with any metal part of the car because it is still connected to the positive side of the main battery.

I have just left the positive connected to the aux.
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EDIT: I want to be clear that this does not disable ESS. Simply disconnecting the AUX battery will disable ESS, but that will throw an error. Doing the following has no affect on ESS, it will continue to work as normal, just off the main battery :). If you want to disable ESS, that is a different subject.\
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Great post, OP! I do wonder - why no just remove the AUX battery from the vehicle entirely? Feels superfluous to be driving around a disconnected battery :)

If you already disconnected the AUX and have the @ alert and start up error, you will have to disconnect the main for a few minutes to reset the error after disconnecting the PCR.
Is disconnecting both batteries really necessary / wouldn't the IBS "relearn" process described here be sufficient: Auxiliary battery
Great post, OP! I do wonder - why no just remove the AUX battery from the vehicle entirely? Feels superfluous to be driving around a disconnected battery :)
If warranty work is needed, the AUX can easily be hooked back up. Plus, if you keep the AUX charged, it can be used to jump start in a pinch if the main is dead. However, my main recently died and I replaced it with a bigger battery and removed the AUX to make room ;)

Is disconnecting both batteries really necessary / wouldn't the IBS "relearn" process described here be sufficient: Auxiliary battery
IDK maybe. When I experimented with my '19 JLUR, I was only able to remove the error with a code reader or by disconnecting the battery for awhile. IBS relearn might work also. ;)[/QUOTE]
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