Jumperless aux battery/PCR bypass

[ShadowsPapa]

So removing the ground and fuse eliminates the aux battery from the circuit. Does the light come on and stay on? It seems like it wouldn't.

Jerry beat me to it - exactly as he said.

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[Geoarch]

Removing the ground is what eliminates the aux battery from the circuit, removing the fuse is what prevents the system from detecting that the aux battery has been removed, keeping the light off.

Thanks Jerry. I have an error light on for the aux, and so I'll try that. I thought I'd wait until my first oil change and let the dealer mess with it, but until then I'll do that. It's charging at a relatively high rate (i.e. 14 v) a lot of the time unless I'm on a long trip, so I assume there is a problem with the aux battery or the electronics. I was a tracked vehicle mechanic, not an electrician. We had guys to do that. Having this forum with guys with different experience probably saves money and headaches.

 

[ShadowsPapa]

It's charging at a relatively high rate (i.e. 14 v) a lot of the time unless I'm on a long trip, so I assume there is a problem with the aux battery or the electronics.

That's normal. Mine spends quite a bit of time over 14 - often at 14.8 in cooler or cold weather. 14.6 isn't too uncommon in the summer, then it winds down.
Long trips see it going into the lower 13s.
Both of my trucks saw 14.6 unless I had JUST driven it on a long trip or charged the batteries.
AGM batteries require a very different charging sequence and voltages than legacy wet cell batteries.
(I started specializing in electric/electronics when my HS auto teacher put me in the ignition and electric side of things in contests)

 

[Geoarch]

That's normal. Mine spends quite a bit of time over 14 - often at 14.8 in cooler or cold weather. 14.6 isn't too uncommon in the summer, then it winds down.
Long trips see it going into the lower 13s.
Both of my trucks saw 14.6 unless I had JUST driven it on a long trip or charged the batteries.
AGM batteries require a very different charging sequence and voltages than legacy wet cell batteries.
(I started specializing in electric/electronics when my HS auto teacher put me in the ignition and electric side of things in contests)

That's good to know. Even when I charge it, it gets up to 14.

"(I started specializing in electric/electronics when my HS auto teacher put me in the ignition and electric side of things in contests)"

Strange how your life takes a certain path with just one thing that happens to you. I was a wiz in high school auto shop (two semesters), rebuilding engines, and building engines and cars for drag racing (street and strip), then when I went into the Marines I finished first in class in tracked vehicle repairman school - what a surprise. I thought briefly of starting my own auto shop when I got out, but used the GI Bill for geology and archaeology since I did so well in chemistry and physics. At least I can find my way around a wrench, as long as it's not too complicated electrically. Many on this forum started similarly, like you, especially we "slightly" older guys. I imagine there is a thing about Jeeps and wrench work. It's addicting and expensive. My wife, an art historian, but pretty mechanically inclined herself, just rolls her eyes. In 1968 I bought a '53 M38-A1 surplus (I was 19) and put a Buick V-6 in it (those small ones), then after Marines bought a new '73 CJ-5 for $3400 bucks! I kept that for 15 years through grad school running around the Southwest and northern Mexico doing fieldwork. Sorry about the digression.

 

[Zilla]

And removing the aux ground is simple as it's one of the cables at the top of the IBS on the crank battery. The other goes to the body ground between battery and fender (at least on the gas versions)

Can someone post a photo of THE "cable at the top of the IBS on the crank battery" that should be removed for this to work properly? Thanks in advance.

 

[Gatorized]

Can someone post a photo of THE "cable at the top of the IBS on the crank battery" that should be removed for this to work properly? Thanks in advance.

The correct cable will depend on your build year and possibly other considerations… best to trace which cable goes to body ground and then disconnect the other one.

 

[ShadowsPapa]

Can someone post a photo of THE "cable at the top of the IBS on the crank battery" that should be removed for this to work properly? Thanks in advance.

2020 Overland SHOULD BE like this - I said SHOULD BE - Easy to check with a meter, though.......

The cable that the battery charger clamp is on goes to the aux battery in the wheel well area. It's held onto the chassis ground cable by that tall stud still on the negative post.

But like suggested - disconnect the first cable as seen here and if you put a meter on that cable and the positive battery post of the crank battery and get 12 volts, then that's the cable going to the aux battery.

 

[Zilla]

2020 Overland SHOULD BE like this - I said SHOULD BE - Easy to check with a meter, though.......

The cable that the battery charger clamp is on goes to the aux battery in the wheel well area. It's held onto the chassis ground cable by that tall stud still on the negative post.

But like suggested - disconnect the first cable as seen here and if you put a meter on that cable and the positive battery post of the crank battery and get 12 volts, then that's the cable going to the aux battery.

Thank you, kind sir.

 

[Lunentucker]

If you want to completely delete the secondary battery and clean up all of the associated junk from it, this video will be a good guide for you to use. It's also the best Genesis installation video I've seen anywhere.



Going through the top isn't generally considered to be the easy way. You can also access the AUX battery via the passenger's side front wheel well, but you have to remove the fender liner to get to it.



If you go that route be prepared to replace a couple of broken fender clips.
https://smile.amazon.com/dp/B07F2MQPL8

 

[Gvsukids]

After doing this, I have the Avengers light on my dash.

 

[Lunentucker]

After doing this, I have the Avengers light on my dash.

I was reading last night that it might take up to five extended power cycles for the battery sensor to reset itself. Not sure if that would trigger the light or not.
The thread on the Wrangler forums seems to be covering the issues better.

 

[ShadowsPapa]

I was reading last night that it might take up to five extended power cycles for the battery sensor to reset itself. Not sure if that would trigger the light or not.
The thread on the Wrangler forums seems to be covering the issues better.

What battery sensor are you referring to?
Not the IBS, surely, as it's got zip to do with anything related to ESS or the aux battery.
And no, it doesn't take that long with the JT - I've got some documents on resetting the IBS and it can happen as quickly as a single afternoon.
The IBS doesn't reset itself anyway - you must totally disconnect it to reset it - remove power from it.

So you must be referring to some other "battery sensor".

Removing the fuse referred to in post 1 simply prevents the PCR from opening.
If it can't open and the system does a quick check of voltage - it's going to be reading the main/crank battery and assume life is good and move forward.
It doesn't "know" that the PCR didn't open because there's nothing about the PCR to sense it's state.
It's normally closed, meaning crank and aux batteries are in parallel.
It quickly opens the PCR and does a voltage check - assuming with the PCR open it's checking the aux battery to know whether or not ESS can function later assuming all of the other 20+ checks pass muster later.
Once that check is done, and it happens fast during a start, then the power is removed from the PCR, allowing it to close and connecting the two batteries together again.

 

[Lunentucker]

I was referring to the IBS, and yes, I meant that it resets after being removed from power.


Like I said, they've covered many of the issues on the Wrangler thread.
The mid year ground cable switch. The IBS issues, and more.

Calm down. Shovel snow or something.

 

[ShadowsPapa]

I was referring to the IBS, and yes, I meant that it resets after being removed from power.


Like I said, they've covered many of the issues on the Wrangler thread.
The mid year ground cable switch. The IBS issues, and more.

Calm down. Shovel snow or something.

Huh? LOL - calm down what? Where you getting that?

I'm just trying to correct the - uh, bad info - that keeps going around about this stuff - stuff that keeps being repeated although purely speculation, guesswork, whatever, and too often wrong.
(such as the incorrect bit "5 power cycles") when the IBS reset has been covered ad nauseam here and other threads.

FACT - it only takes a couple of starts with about 3 hours sitting in between. It usually learns in a single morning or afternoon.
Fact -
IBS reset and subsequent relearning have nothing to do with the ESS or the ESS light being on. IBS is only concerned about the main battery amp hours out, amp hours in, and it has no impact on the aux battery or the ESS.

The ground cable change was also covered here multiple times and we've shown how to determine which is which. It's simple with a volt meter.

For those who believe this hasn't been covered well enough in these forums and/or who prefer the executive summary -
IBS reset - takes only a few minutes of being disconnected to force it to reset and forget everything stored in the IBS (BUT - the PCM and BCM have the info the IBS has fed them)
IBS relearn - takes a start, about 3 hours sitting with nothing going in and only normal draw coming out, and usually a second start, for it to relearn.
IBS doesn't impact **ESS or any dash lights. (** it can cause ESS to not stop the engine if it has reported low voltage, excessive battery temperature and so on, but doesn't trigger dash lights)
IBS tells the BCM about power taken from the crank battery, power going into the crank battery, battery temperature and similar information.
IBS cannot report on the aux battery because the aux battery bypasses the IBS.

the larger gauge cable is the main ground cable.
The smaller cable is the aux battery ground.
Easy to determine which is which -
Take the top cable off the top of the IBS. The top cable is the one held onto the taller stud of the two.
Volt meter between main battery positive and the cable you just removed -
If you get 12+ volts, that is the aux battery ground cable.
If you get only a couple of volts, and perhaps some sparks, then it is the main battery ground cable to the chassis and block.
Remove the lower cable that's connected directly to the IBS via the shorter stud,
Connect volt meter to that and the main battery + terminal.
12 volts should be seen, indicating THAT is the ground cable from the aux battery.

 

[ShadowsPapa]

After doing this, I have the Avengers light on my dash.

As your HS teacher may have said once - "recheck your work".
That light is usually caused by it believing the aux battery has a problem or there's a hard failure. I've got a list on my server in the house as far as possible causes - if I can find it among the mess of FCA docs I have.
I had my 2020 apart multiple times to diagnose, measure, charge batteries and so on - never once had the light come on, or any other light for that matter. You can disconnect thing for hours and as long as things go back correctly, it's going to not trigger any lights.
The worst I ever saw was that the ESS didn't work for a short time after putting it back together. (but you don't care about that). No lights, ever.

It is truly simple - and as Jerry has said -

Removing the ground is what eliminates the aux battery from the circuit, removing the fuse is what prevents the system from detecting that the aux battery has been removed, keeping the light off.

Just be really sure to remove the correct ground, and correct fuse.

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