Diagnostic tools for start stop system not working

[BlueCT]

For the best couple weeks my start stop system unavailable light is on. In the menu it days system unavailable service system. I hate this system and don't mind it not working, however, I do want to know why it's not working. I brought the truck to the dealer for an oil change and they want a $395 diagnostic fee. I put a $30 ODB2 reader on it and there were no codes. I have a couple questions. 1) would a more expensive tool in the 300 $500 range give me details and if so which tool, 2) is there a process I can go through on my own to diagnose this issue without very expensive computer diagnostic equipment. 3) is there a specific common issue with the start stop. I checked old posts and I see the aux battery as a common issue. I don't think it's that because I had that about 18 months ago and the menu said something about charging which it's not saying this time. 18 months ago the dealer changed both batteries under warranty and I put a charger on and the issue persists. Maybe it's still battery but I don't think so. Any help is appreciated.
Thanks
Chris

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[Lunentucker]

1. No
2. Yes - bypass the aux battery
3. Yes. See 2

 

[BlueCT]

Thanks for your reply. When I had the issue previously with the start stop system is was the aux battery. That said last time it said something like system charging Starr stop unavailable. There is no mention of charging this time. Also, last time putting a battery charger on the car fixed the issue for a couple days this time I did not. I'm curious given my circumstances if others still think it could be the aux battery. How long does it take to disable the aux battery?

 

[Dakarra]

Not sure how your 2014 JKU is set up compared to my JT, but when I had that problem it was the auxiliary battery. Dealer replaced it and it has been fine since (PS, I don't like the auto stop-start feature, either and didn't mind it not working - but the fact that there was a problem "with something" made me nervous).

 

[Lunentucker]

Thanks for your reply. When I had the issue previously with the start stop system is was the aux battery. That said last time it said something like system charging Starr stop unavailable. There is no mention of charging this time. Also, last time putting a battery charger on the car fixed the issue for a couple days this time I did not. I'm curious given my circumstances if others still think it could be the aux battery. How long does it take to disable the aux battery?

Minutes.
1. Disconnect the aux ground at the main battery ground group.
2. Tape the end to prevent incidental grounding and secure with zip ties.
3. Remove fuse F42

If you have no power at all, you removed the wrong cable. Swap them.
If you lose all power, your subscriptions and icons on the screen may be temporarily lost. They'll come back after a few hours. Overnight at worst.

The only sure way to test both batteries is to separate them and charge/test each one independently. Except during ESS, they are linked as one, and if one is failing it can purge the other one by constantly trying to recharge from it.
It's a stupid system, and isolating the main cranking battery from the aux cuts your failure chances in half, AND it allows you to independently gauge the veracity of the main battery - the one that gets you home.

Ignore the part in the video about this disabling ESS. that was wrong. ESS will still function, but just use the main battery.
You can disable it by other methods and devices.

 

[BlueCT]

Thanks, I think I will give this a try. If I do this do you think I need to leave the batteries disconnected to "reset " anything to get rid of the ess unavailable error?

 

[Mr._Bill]

Thanks, I think I will give this a try. If I do this do you think I need to leave the batteries disconnected to "reset " anything to get rid of the ess unavailable error?

The ESS unavailable message is usually the result of an electrical issue. It will reset when the issue is resolved. It can be caused by other issues, such as a misfire, but is typically battery related.

First step is to separately charge each battery and reset the IBS. If the batteries are still good, this should solve the problem. If not, my next step would be to replace both batteries with something better than what Jeep provides.

I prefer these:

ACDelco Gold 94RAGM (88864542) 36 Month Warranty AGM BCI Group 94R Battery https://a.co/d/9UPDdDG

ACDelco Gold AUX14-200 36 Month Warranty Auxiliary AGM 200 CCA Battery https://a.co/d/9CIOhMv

 

[BlueCT]

Thanks for the advice. I just did the aux battery bypass and I’m still getting the error. Since both batteries are less than 18 months old I didn’t think this was the issue. I will charge the main to make sure but its read 12.8 volts when off so I think its good. Any other ideas?
Thanks
Chris

 

[Lost1wing]

Thanks for the advice. I just did the aux battery bypass and I’m still getting the error. Since both batteries are less than 18 months old I didn’t think this was the issue. I will charge the main to make sure but its read 12.8 volts when off so I think its good. Any other ideas?
Thanks
Chris

Assuming you did the Aux delete.


Example: If you aux was bad, it was dragging down your main. Recharge the main battery reset your IBS.

If you main battery was bad, deleting your Aux battery didn't help. Have your main battery tested or replaced. Charge the new battery fully. Do not assume it is fully charged just because it is new. Reset the IBS.

Now if you smoked the fuse array during your delete or prior testing, you will need to do some more testing with a meter.

 

[Mr._Bill]

Is it still within the 3/36 warranty?

Did you purchase an extended warranty?

 

[BlueCT]

It is not still under warranty. I haven’t had a chance to charge it yet but I did drive it for two hours today. I did the aux delete so if it’s anything it’s the main but I don’t think it is that. About a week before this light came on I started the truck and the idle seemed rough but I was in a hurry so I just drove it and didn’t think about it again. Next day same thing. I got on here and I read some old post and someone suggested driving the truck hard ie high RPMs etc to see if that clears the rough idle. I did that and it seemed like that fixed it but then a couple days later this issue occurred. I don’t know if this is related but I’m guessing it is I just don’t know what to look at. By far the most posts on here are about bad batteries and the others seem to be about a misfire issue. My code scanner says there are no reported misfires but I’m not sure really what that means as I haven’t really used a code scanner before.
-Chris

 

[ShadowsPapa]

It is not still under warranty. I haven’t had a chance to charge it yet but I did drive it for two hours today. I did the aux delete so if it’s anything it’s the main but I don’t think it is that. About a week before this light came on I started the truck and the idle seemed rough but I was in a hurry so I just drove it and didn’t think about it again. Next day same thing. I got on here and I read some old post and someone suggested driving the truck hard ie high RPMs etc to see if that clears the rough idle. I did that and it seemed like that fixed it but then a couple days later this issue occurred. I don’t know if this is related but I’m guessing it is I just don’t know what to look at. By far the most posts on here are about bad batteries and the others seem to be about a misfire issue. My code scanner says there are no reported misfires but I’m not sure really what that means as I haven’t really used a code scanner before.
-Chris

There are over 32 different criteria that need to fall in line for the ESS to work. there's no simple diagnostics other than the tools the dealership has.

Likely your rough idle is part of the issue. A misfire will cause errors and the ESS to stop working (say "not available")

Gotta stop relying on the "old posts" stating "the aux battery is the issue" as most of those are wrong. Can be over two dozen issues from transmission to engine.
Voltage isn't the only reason it won't work. You can have two perfect batteries and it may still fail.
Pulling/disconnecting the aux battery is often masking underlying issues.
It's like taking tons of pain killers instead of finding out why your gut hurts so bad - could be ulcer or cancer or that taco you ate.

Time to diagnose - find out why you are having other issues and the ESS issue may simply go away because it wasn't working due to the other things.

Too often it's yank this, pull that - and the whole issue is a misfire or something totally unrelated to the battery.
It's not always a voltage issue.

It's a simple place to start - but use a meter and check the voltage and don't assume.

 

[BlueCT]

Thanks, I agree. I know it's the battery for a lot of people, it was for me a while ago it's not this time. I put a code scanner on it and didn't get a code. I put a different scanner on and I saw 1 count of a misfire. What seems like an interesting data point is when I bypassed the 2nd battery I used a procedure that I believe you posted on resetting the device attached to the main battery terminal, I forget the name. Both batteries were disconnect from the car and the entertainment system even went to its default startup settings. But 2-3 seconds after starting the car the same start stop unavailable light came on. Almost like the car has something permanently wrong vs something that happens while running that causes the issue. Unfortunately, my local dealer decozen jeep has really been terrible with service so I need to find a good local dealer in north NJ to go to.

 

[BlueCT]

So many people on these forums have been helpful to me that I thought I would post to close the loop on this now that I finally figured it out. It was the main battery not AUX battery. I truly did not think it was a battery until I realized that whenever the truck sat for several hours the dash screen displayed voltage regardless of whatever screen it was on when the truck was shutoff. I tried to charge the battery and that didn’t fix it. At the recommendation of someone on here I disconnected the battery and reset the voltage regulator (i think that is what it’s called, the little box on the negative terminal). That didn’t work. I isolated and bypassed the aux battery and charged the main battery again. Still no luck. Then I realized my battery charger (Noco genius 10) has a repair function . I tried that and that finally fixed the issue. I truck is 4.5 years old and this will be the 2nd battery to cause the start stop to fail. Really the 3rd because both the main and the aux battery caused a failure when I first got the truck.
I think I will probably go to one of the dual battery setups at some point. I should have just replaced the main battery but I just couldn’t bring myself to do it since it was only 18 months old. Certainly a learning experience for me, and I hope for others as well.
-Chris

 

[ShadowsPapa]

It's always the aux battery! Just read any Jeep forum.
I read it on the internet in a Jeep forum, so I know it's true (hahaha - sarcasm)
it causes global warming, misfires, flat tires, broken axles, bubbling paint and cracked windshields. That's how some make it seem.

And yet - it's also often the main battery.
Or maybe it's something totally different - like in my case of my 2020 - I charged each independently, reset the IBS (that box on the negative battery post and life went on with ESS and all else working perfectly.

Over 32 possible reasons for the ESS to not work, including engine or transmission issues, ABS issues, torque on the steering input (yeah, when you hang your hand on the steering wheel) and more - but it's the aux battery, just ask 'em.
It's quite entertaining, actually.

Chevrolet, BMW, Mercedes and other companies have used the dual battery ESS system - with a smaller auxiliary battery. But according to the internet - it's a Jeep design.

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