Another ESS/Battery Question

[Panthers65]

I've ready several of the other threads out there about the Main/Aux Battery, but can't find anything specific to my situation.

'21 Sport S with a S-Tech switch box and a winch. Gladiator was delivered November '21, so 14 months old, and when it was delivered there was an issue with the ESS and the dealership replaced the Aux Batter before I took delivery. ESS worked fine for about a year, and stopped working a month or so ago. Secondary vehicle, a lot of around town trips which I know is rough on a battery.

Getting a plain "Engine Start/Stop Not Ready" message, no other messages/reason.

Engine off, last drove it for a few miles last night:
Voltage across the main battery- 12.4-12.5
Voltage at the N1 Terminal- 11.6

Engine on, right after start:
Voltage across the main battery- 14.7
Voltage at the N1 Terminal- 14.7
Voltage on the dash screen- 14.6

After letting the truck idle for 10 minutes and come to temp, all the voltages are the same , maybe .1V higher. With the switches and winch, I figured the dealership might hassle me about warranty work, so if it's just the Aux battery I'd likely just replace it or bypass it all together myself. Given the low voltage on the N1 terminal with the engine off, and the running voltage staying at 14.7, that would be my assumption. Can anyone confirm if I'm on the right track?

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[IanNubbit]

To be extremly accurate. Go ahead and pull the line off N1 all together and then test the voltage. That will be more accurate. But that is indeed looking like an AUX battery with low voltage

 

[Andy29847]

The voltage at N1 and the main battery should be the same unless you separated the 2 batteries by removing the aux battery negative cable. If the batteries are still connected together and the voltage is that different, you have a cable or cable connection problem.

 

[ShadowsPapa]

To be extremly accurate. Go ahead and pull the line off N1 all together and then test the voltage. That will be more accurate. But that is indeed looking like an AUX battery with low voltage

Yeah, like he said. Normally the voltages will be the same or close to it because the batteries are in parallel when the truck is off, so you see the combined/average voltage of both.
That low at N1 is indicating a weaker aux battery but then it's under load, the truck's computers and stuff pulling from it while at rest.

It might also be worth checking the high current fuse to ensure the aux battery is being charged, and the PCR to make sure it's actually connected and not open or burned contacts.

A 0.8 volt drop is a lot between the two.

 

[ShadowsPapa]

The voltage at N1 and the main battery should be the same unless you separated the 2 batteries by removing the aux battery negative cable. If the batteries are still connected together and the voltage is that different, you have a cable or cable connection problem.

That was also a thought I just posted as yours came in. Is the PCR actually closed and contacts not burned?

When in parallel there should be very little difference unless there's a lot of resistance or an open between the two.

In fact, mine shows only about 0.1 difference - and my 2020 when the ESS wasn't working before I reset the IBS and independently charged both batteries didn't have that sort of difference.

 

[Lost1wing]

I think someone here said to separate the batteries and charge them up separately. That way you would have a better understanding of who the culprit is. 11.6v is pretty low. One of the two is not healthy. Replacing both is recommended. If under a warranty still, why not let the dealer look at it? I'm with you if you don't trust the dealer experience.

 

[ShadowsPapa]

I think someone here said to separate the batteries and charge them up separately. That way you would have a better understanding of who the culprit is. 11.6v is pretty low. One of the two is not healthy. Replacing both is recommended. If under a warranty still, why not let the dealer look at it? I'm with you if you don't trust the dealer experience.

EASY to do by pulling the cables off the top of the IBS and then disconnecting those black cables from each other. Easier with 2020 because the aux battery ground is the top cable. 2021 and later the aux battery ground is the one right on top of the IBS.
You connect the + for charging both to the + of the main battery, and the negative/- of the charger either to the top of the IBS for charging the main battery, or to the end of the aux battery ground cable to charge just that battery.

I would disconnect the connection at N3.
Check the voltage at the stud of N3 and you should see battery voltage. If not, then that fuse is bad.

 

[Panthers65]

Did a quick Aux battery delete (pulled the F42 fuse and disconnected the Aux Ground from the main battery)

Quick 5 mile drive, No lights or anything on the dash, but still getting the "Start/Stop Not ready" Message. I noticed the Volts moving around while I was driving, around 14.5V while moving, would jump between 13.5 and 14.5 when sitting at a red light/stop sign.


I'm beginning to think it's the IBS Sensor, is there another way to reset this besides the disconnect it and then drive normal for 4-5 days? seems like a long process to diagnose.

I"m also concerned about the voltage difference between the N1 and the Battery, going to hook the Aux batter back up and check for lose wires- anywhere specific I should be looking?

 

[Panthers65]

I think someone here said to separate the batteries and charge them up separately. That way you would have a better understanding of who the culprit is. 11.6v is pretty low. One of the two is not healthy. Replacing both is recommended. If under a warranty still, why not let the dealer look at it? I'm with you if you don't trust the dealer experience.

No issue with trusting the dealer, I just don't want to pay them a diag fee just to have them tell me they won't warranty anything because I have the s-tech switches or the winch.

 

[Panthers65]

I would disconnect the connection at N3.
Check the voltage at the stud of N3 and you should see battery voltage. If not, then that fuse is bad.

I know N1 goes to the sensor for the Aux Battery, where/what does N3 go to?

 

[ShadowsPapa]

I'm beginning to think it's the IBS Sensor, is there another way to reset this besides the disconnect it and then drive normal for 4-5 days? seems like a long process to diagnose.

I"m also concerned about the voltage difference between the N1 and the Battery, going to hook the Aux batter back up and check for lose wires- anywhere specific I should be looking?

No it's not the IBS. It doesn't cause that sort of thing. All it does is record information and send it via the LIN bus to the BCM, etc.
The PCM determines the output of the alternator.
And resetting it takes only disconnecting it, waiting 10-15 minutes, and putting it all back in place/reconnecting.
Are you SURE you removed the correct ground from the main battery?

I know N1 goes to the sensor for the Aux Battery, where/what does N3 go to?

N1 is from aux battery - to the truck's electronics and cluster and inside systems.
N3 is how the aux battery gets charged. N3 is a fuse from the high current fuse bus -
Alternator connects to the high current fuse array, N3 terminal is one of those fuses - going to the aux battery to charge it.
If N3 fuse is blown, the aux battery can't charge.

Stop/start not ready can mean a lot of things - including issues that are totally not related to the batteries.

 

[Panthers65]

No it's not the IBS. It doesn't cause that sort of thing. All it does is record information and send it via the LIN bus to the BCM, etc.
The PCM determines the output of the alternator.
And resetting it takes only disconnecting it, waiting 10-15 minutes, and putting it all back in place/reconnecting.
Are you SURE you removed the correct ground from the main battery?



N1 is from aux battery - to the truck's electronics and cluster and inside systems.
N3 is how the aux battery gets charged. N3 is a fuse from the high current fuse bus -
Alternator connects to the high current fuse array, N3 terminal is one of those fuses - going to the aux battery to charge it.
If N3 fuse is blown, the aux battery can't charge.

Stop/start not ready can mean a lot of things - including issues that are totally not related to the batteries.

Yes, I'm sure I disconnected the right negative, my jeep is a late model '21 where the ends are switched, I removed the "L" shaped wire with the stud on it, the wire with the smaller diameter. (https://www.jlwranglerforums.com/forum/threads/ess-battery-cable-change.86624/)

Normally I see a "Start/Stop Not Ready" and then a message (IE "Cabin Heating/Cooling" "Driver Door Open" or "Driver seat Belt not connected".

Just went out and measured the voltages again after my drive, With the F42 fuse pulled and the Aux negative unhooked, I'm getting 12.5V across the main battery, as well as at N1 and N3? It's possible I wasn't getting a good reading at the N1 terminal the first time.

Where would that leave me with what else to check. I"m going to put the Aux Battery back in the system and see if it's the same.

 

[ShadowsPapa]

What I would do if it was mine -
I would fully charge the main battery with a good AGM charger of 10 amps or more.
I would then fully charge the aux battery with same charger.
While those were charging, I'd set the IBS off to the side, disconnected.
Once both batteries were charged, I could check the voltage of each.
I'd make note, and connect it all back together.
After the IBS is reset (and that's what you did if you did the above steps) it may take a couple of starts and shut downs, and 2 or 3 hours of just sitting with nothing going on, but by then the IBS should have relearned.

As to the stop/start not ready message - it will say not ready and not tell you why for about 2 dozen reasons - CAT not up to temperature, air pressure, brake system pressure, ABS issues, maybe some codes stored, and so on. I had misfired but NO CEL and mine simply said "not ready" with no reason. Once the misfire code was cleared (even though there was no CEL) then things worked ok.
It will tell you about some things, but that's the minority of things - things you'd know about like steering wheel angle, for example.
If it's in 4 wheel drive it may not function, if it thinks it's towing, it won't function - but not tell you why.

(Best to do IBS reset with fully charged battery....... not if the batteries aren't fully charged at full voltage)

 

[Panthers65]

What I would do if it was mine -
I would fully charge the main battery with a good AGM charger of 10 amps or more.
I would then fully charge the aux battery with same charger.
While those were charging, I'd set the IBS off to the side, disconnected.
Once both batteries were charged, I could check the voltage of each.
I'd make note, and connect it all back together.
After the IBS is reset (and that's what you did if you did the above steps) it may take a couple of starts and shut downs, and 2 or 3 hours of just sitting with nothing going on, but by then the IBS should have relearned.

As to the stop/start not ready message - it will say not ready and not tell you why for about 2 dozen reasons - CAT not up to temperature, air pressure, brake system pressure, ABS issues, maybe some codes stored, and so on. I had misfired but NO CEL and mine simply said "not ready" with no reason. Once the misfire code was cleared (even though there was no CEL) then things worked ok.
It will tell you about some things, but that's the minority of things - things you'd know about like steering wheel angle, for example.
If it's in 4 wheel drive it may not function, if it thinks it's towing, it won't function - but not tell you why.

(Best to do IBS reset with fully charged battery....... not if the batteries aren't fully charged at full voltage)

Got it! Weekend project.

Would a tazer read the codes if there was no CEL? Haven't noticed and poor running conditions

 

[IanNubbit]

Lot of info going back and forth. You most likely saw the low voltage while still plugged in was because of the resitance of the main battery power leading its was back instead of coming from the AUX battery. That voltage was realistically much lower. Also you did the right thing by bypassing the battery. as long as you also jumped N1 to N2 or N3 i always forget. The system will say not ready charging till the IBS is above 70%. This will happen over time while the vehicle is running and while sitting undisturbed for hours. If the main battery is good and charged, the sensor will read correctly by the morning

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