Auxiliary Battery Message

[jimim]

I have read multiple threads about this message but I wanted to see if anyone had any inside on my exact situation.

My dealer is 90 mins away. I do trust them.

Message came on a few weeks ago. They said with 40k on the jeep have the aux battery swapped out vs driving down for now. Prob battery. I did that at my Chevy dealer cause I trust them.

Week ok. No message. Went away for 5 days and came home to message again.

Jeep kept in heated garage at night and I drive all day for my job in and out of homes all day.

When I start in morning the voltage is 12.2 when I turn the jeep over and it climbs to 14.1-14.4 as I drive WITH THE AUTO START STOP OFF. At red lights I stay at 14 plus. When I stop and then restart after leaving a house the battery has been reading 12.2'ish and climbs right to 14 in like 3 secs always.

When I have auto start NOT OFF and it kicks in at a red light my voltage drops to 11. something- 12. something and I cattail get like a blink on and off on my radio or I hear a quick static in the speakers real quick. Once motor kicks in again climbs to 14 plus. This doesn't always happen. Sometimes auto start stop doesn't even kick in like it usually does.

I'm going down to jeep this weekend. They said now I have to come in.

They said:

1. bad aux battery
2. bad main battery
3. sensor issue
4. bad alternator

All possibilities. They said putting it on the computer will tell us what it is.

Guys what is your opinions. What other stuff can be going on? Can it be the alternator?

Thanks, I just want to educate myself when I go down. I'm a physical therapist. I don't know anything about trucks or cars. I drive them.

Thanks so much,
Jim

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[Stuckinthesand]

90% chance it is just a bad aux battery. They should replace both the aux and main battery as once the aux goes bad it starts to take the main with it. 99% of electrical issues can be traced back to a bad aux once you start getting that message. Factory batteries that came with them are crap.

 

[jimim]

90% chance it is just a bad aux battery. They should replace both the aux and main battery as once the aux goes bad it starts to take the main with it. 99% of electrical issues can be traced back to a bad aux once you start getting that message. Factory batteries that came with them are crap.

ok so even though I replaced the aux a week ago or so? main battery was never replaced yet. 40k miles on the jeep.

 

[kah.mun.rah]

My vote is a bad main battery

 

[Reinen]

The main an aux are linked 99.9% of the time. You should consider them the same battery. Right now you have a half new, half old battery. Which is stressing your new battery. Replace the main too.

 

[jimim]

ok guys. i appreciate that. that makes good sense to me. i knew they were links but didn't know they pretty much were relating on each other kinda.

i appreciate everyones opinions a lot.

 

[UncleJimmy]

Having just gone down this rabbit hole myself, the first thing I would recommend is to familiarize yourself with the ESS/battery system. The AUX batteries tend to not last long and can drain the starting battery as well as cause a host of other electrical gremlins. It's also easy to blow a fuse if you or someone else doesn't know that with the main battery terminals disconnected the leads are still hot from the AUX and if the pos touches anything grounded in the engine compartment it can blow the fuse on the fuse array. Many carry a spare fuse array ID: 68368854AA. I would also recommend to bypass the AUX battery.

https://www.jlwranglerforums.com/fo...-cable-caution-and-ess-n3-fuse-warning.66247/

Also note that fluctuating voltage is normal as this is an intelligent charging system in the Jeep. If you disconnect battery or IBS sensor, the system needs to relearn and will default to 14+v for a day or two until it relearns. So just ignore that unless you are seeing really low voltages (below 12). But normally you will see voltages fluctuate as you drive in the 12-14v range.

Most times it's batteries, but in my case it turned out to be a bad hood plunger/sensor (one of the two hood plungers).

There are at least three ways to bypass or delete the AUX. This way is easy to revert back to stock in case of warranty work:

 

[jimim]

should it drop below 12 a bit when auto start stop is on and kicks in at a red light? like i said i noticed that today only with auto start stop on. when its off a stay at 14 at red lights. but again this drop only happened 4 times already 3 times before swap of aux battery and once today with new aux battery.

 

[UncleJimmy]

should it drop below 12 a bit when auto start stop is on and kicks in at a red light? like i said i noticed that today only with auto start stop on. when its off a stay at 14 at red lights. but again this drop only happened 4 times already 3 times before swap of aux battery and once today with new aux battery.

I am not 100% sure, so I don't want to speculate. Maybe someone else can chime in on that.

I would recommend studying that post I linked to; that has basic info on how the system works and how to easily test alternator and fuse array etc.

You can always go to AutoZone and have the batteries tested (you will need to learn how to isolate and test the AUX battery), or, and what I would do if the batteries are a few years old already is to bypass or delete the AUX and put in a good quality H7 main battery. If you want to keep the ESS feature and the AUX then replace both batteries. Lastly, if the warning is still on then I would try checking/swapping the two hood sensors. Hope that helps.

 

[Fudster]

My vote is a bad main battery

If I may build on this @jimim my vote is either a bad main battery or one that is about to become part of a overall bad battery system of two batteries as the old main battery risks catabolizing your new Aux one.

Unfortunately, best practices have found us dual AGM battery JL owners replacing both batteries when either one is in need of replacement. This goes to @Reinen's point about how those batteries are connected in parallel 99% of the time (but for an instant at cold crank and during ESS events.)

An analogy: a medical emergency for one of a pair of conjoined twins, is a medical emergency for both due to their shared, even if only in part, anatomy/blood vessels, etc.

 

[jimim]

If I may build on this @jimim my vote is either a bad main battery or one that is about to become part of a overall bad battery system of two batteries as the old main battery risks catabolizing your new Aux one.

Unfortunately, best practices have found us dual AGM battery JL owners replacing both batteries when either one is in need of replacement. This goes to @Reinen's point about how those batteries are connected in parallel 99% of the time (but for an instant at cold crank and during ESS events.)

An analogy: a medical emergency for one of a pair of conjoined twins, is a medical emergency for both due to their shared, even if only in part, anatomy/blood vessels, etc.

totally makes sense. i would have totally done that if they said to. again my fault also cause i didn't drive down but i figured 3 hours of driving vs 120 for a new mopar battery was a fair swap to see if it was the fix. but if i knew this first i would have done both.

 

[jimim]

I am not 100% sure, so I don't want to speculate. Maybe someone else can chime in on that.

I would recommend studying that post I linked to; that has basic info on how the system works and how to easily test alternator and fuse array etc.

You can always go to AutoZone and have the batteries tested (you will need to learn how to isolate and test the AUX battery), or, and what I would do if the batteries are a few years old already is to bypass or delete the AUX and put in a good quality H7 main battery. If you want to keep the ESS feature and the AUX then replace both batteries. Lastly, if the warning is still on then I would try checking/swapping the two hood sensors. Hope that helps.

im going to study that tonight when im on a larger screen. i appreciate that very much cause i don't know how it is actually wired.

 

[rhocking]

When I start in morning the voltage is 12.2 when I turn the jeep over and it climbs to 14.1-14.4 as I drive WITH THE AUTO START STOP OFF. At red lights I stay at 14 plus. When I stop and then restart after leaving a house the battery has been reading 12.2'ish and climbs right to 14 in like 3 secs always.

I get 12.7V when I press the start button without starting the jeep. This drops to 12.2V when starting. It goes to 14.3V when driving short distances. The 14.3V reflects the alternator recharging the battery. After driving for a while (30 miles or so) this will drop to the 13.7V-13.9V range as the battery charges up. I seldom drive for several hours to see if this drops under 13V after fully charged but I believe others will tell you this is what will happen.

The recommendation is always to replace both batteries at the same time because in the 'joined' ESS system the weaker battery (normally the Aux) will pull down the stronger battery.

I would recommend going for a bigger Main battery (if you don't have one already due to the towing package).
See: https://www.jlwranglerforums.com/fo...replacement-talk-jl-jt-🪫.100534/#post-2082809

I would also recommend taking the Aux battery out of the picture.
See: https://www.jlwranglerforums.com/forum/threads/jumperless-aux-battery-bypass.95945/

The process for taking the Aux out of the picture (not removing the Aux battery) takes less than 5 minutes. You have a new Aux so it is not vital to take the Aux out of the picture but I think it is a good idea since you then eliminate the smaller battery draining your new main battery.

If you do use the fuse F42 procedure described in the Aux thread I would also recommend you trickle charging the Aux periodically to keep it as a backup. Since you are starting with a new Aux I would hope you might see >3-5 years before it starts to lose charge.

The only downside to all my recommendations is that you will need to turn off the ESS each time or get yourself a smart-stop start or a Tazer to do it for you. If you like ESS (I don't) you also may not want to do the Aux bypass and may want to keep the 'joined' ESS system but will have to realize that the smaller Aux is going to pull down your Main at some point and you will have to replace batteries more frequently.

 

[jimim]

Awesome advice. I have two package so I assume I have larger battery then? I tow a boat.
I’m going to keep the aux in the mix till I get it all 100 percent squared to normal and then go from there.

 

[rhocking]

Awesome advice. I have two package so I assume I have larger battery then? I tow a boat.
I’m going to keep the aux in the mix till I get it all 100 percent squared to normal and then go from there.

Pretty sure the tow package already comes with the Group 94R vs Group 48 battery and also has a slightly higher amp alternator. I think if you replace the main it would most likely clear up your problems and then after you have ESS working you might want to read the thread on doing the Aux battery bypass and determine if this easy fuse (F42) removal and cable disconnect is appropriate for your needs.

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