Service Start/Stop System

[Mwclark]

I have a 2020 JL that I bought used last year. About 3 months ago the light came on for the Start/Stop System. I have a JScan and decided to run the diagnostics to see if there were any error codes. It showed two. One from the Electric Power Steering stating system voltage-circuit voltage below threshold and the other from the Powertrain Control stating battery “b” state of charge performance. The main battery was changed just before I bought the Jeep last summer. I don’t know how old the auxiliary battery is. If it is failing could it be causing the error codes? I did bypass the auxiliary battery by pulling the fuse and disconnecting its negative cable from the main battery but that didn’t help.

Thanks in advance for any information

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[Reinen]

Your batteries are bad. This is what happens when you only change one and not the other. The older battery will kill the new battery. Don't do that.

Replace both Main and Aux at the same time and you'll be fine for a good while.

 

[azjl#3]

Bad batteries.

 

[BXFXJeep]

bad previous owner that only changed the main battery.

 

[linuxos77]

I'm getting the exact same warning (Service Start/Stop System), don't know about any codes as I don't have a tool for that. It's been like this since August after sitting for 3+ weeks getting the blistered paint on doors/hinges done. At 61k miles and both batteries original I'm sure that's the root cause. I think I'm going to bypass the aux and get a really good new main battery and go with that. Just seems like a weird design asking for these troubles. Our lowly Renegade is on the single original battery at 100k miles and has ESS (and never had blistering paint either)......

 

[Mwclark]

Yes, this system seems to cause more issues and build quality has certainly gone down hill the last few years. Especially the early Covid years.

I'm getting the exact same warning (Service Start/Stop System), don't know about any codes as I don't have a tool for that. It's been like this since August after sitting for 3+ weeks getting the blistered paint on doors/hinges done. At 61k miles and both batteries original I'm sure that's the root cause. I think I'm going to bypass the aux and get a really good new main battery and go with that. Just seems like a weird design asking for these troubles. Our lowly Renegade is on the single original battery at 100k miles and has ESS (and never had blistering paint either)......

 

[Mwclark]

Thank you everyone for the replies. It did confirm my suspicions it was auxiliary battery related. I was hoping bypassing the auxiliary battery would clear it up. Maybe if I reset the codes with JScan? I need to figure out how to do it. I also need to disable ESS with JScan if that’s an option.

 

[DaltonGang]

Thank you everyone for the replies. It did confirm my suspicions it was auxiliary battery related. I was hoping bypassing the auxiliary battery would clear it up. Maybe if I reset the codes with JScan? I need to figure out how to do it. I also need to disable ESS with JScan if that’s an option.

Do the Aux bypass, and replace the main battery at the same time.

 

[GaJeepReLAXing]

Do the Aux bypass, and replace the main battery at the same time.

Does anyone know what this is? It’s on the Beatrice battery post and what was bolted down. I disconnected the positive and negative and pulled the fuse… just not sure what to do with this?

 

[GaJeepReLAXing]

Does anyone know what this is? It’s on the Beatrice battery post and what was bolted down. I disconnected the positive and negative and pulled the fuse… just not sure what to do with this?

 

[DaltonGang]

Mopar Battery Sensor

 

[GaJeepReLAXing]

Mopar Battery Sensor

So it needs to stay? Does it need to stay hooked up? How do you disconnect the auxiliary battery then?

 

[DaltonGang]

So it needs to stay? Does it need to stay hooked up? How do you disconnect the auxiliary battery then?

Leave it alone. Read this thread. First few pages are the key pages.
https://www.jlwranglerforums.com/fo...sing-the-aux-battery-easiest-solution.100296/

 

[GaJeepReLAXing]

Leave it alone. Read this thread. First few pages are the key pages.
https://www.jlwranglerforums.com/fo...sing-the-aux-battery-easiest-solution.100296/

So I had unhooked the positive to the six battery as well and Jeep wouldn’t start. Hooked the positive back up and every things work like a champ.

I had already pulled the #42 fuse… so we will see. I’m also going to access my canbus behind the glove box and push all white connectors in…. And buy a spare canbus as a risk aversion step.

thanks for the input and the link

 

[DaltonGang]

So I had unhooked the positive to the six battery as well and Jeep wouldn’t start. Hooked the positive back up and every things work like a champ.

I had already pulled the #42 fuse… so we will see. I’m also going to access my canbus behind the glove box and push all white connectors in…. And buy a spare canbus as a risk aversion step.

thanks for the input and the link

It will not work, if you don't have the update from the dealer, that allows the vehicle.to start when the Aux Battery is malfunctioning. I don't recall what it was. I had my JL updated a year or so, after buying it. I know a friend who had to have the update, and that solved several issues, and allowed him to also do the bypass.

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