An ESS mystery...

[Opus]

I posted recently that the ESS in my 2023 Jeep had stopped working. There have been no warning lights or any other indicators of any problems. I don't have a Tazer installed or any other device like that installed. The Jeep just stopped shutting off at stop lights. Initially when I first noticed it we were in the depths of winter, so I assumed the Jeep kept running to keep the climate control working. But then, once the weather started warming up (we've had days in the 70s and 80s), the ESS still didn't kick on. Some days I would turn the climate control off and just have the windows down and the ESS still wouldn't kick on. At that point, I assumed that the auxiliary battery must be giving out but, again, there have been no warning lights or any other problems. The Jeep always fires right up.

Then, after a few months of the ESS not working, on my way in to work today the ESS suddenly started working again.

So what's changed?

The only thing that has changed is that on Saturday it was hot day, so I ran the A/C for the first time this year but the ESS didn't kick on then, only this morning. And I can't figure out how that would suddenly wake up an ESS that had been dormant for months in all kinds of weather.

Any ideas?

Sponsored

 

[The Last Cowboy]

Your batteries are dying. In a week, or a month, your Jeep just wont start at all. I would suggest a new H7/94R main battery, and eliminating, or disconnecting the auxiliary battery.

 

[TheBirdie72]

This is exactly what happened to my Jeep. Got it in 2021… ESS worked normally for the first few years… then nothing. No warning lights. Jeep just started up and ran just fine with zero ESS for the next couple years. Then after over two years of ESS free operation, it started working again for no reason… for about a month. Then finally got a service start-stop message on dash. Aux battery was finally dead; replaced both batteries a few months ago (little guy was vamp’ing the bigger guy). Now back to “standard-normal” ESS operation again.

 

[Opus]

This is exactly what happened to my Jeep. Got it in 2021… ESS worked normally for the first few years… then nothing. No warning lights. Jeep just started up and ran just fine with zero ESS for the next couple years. Then after over two years of ESS free operation, it started working again for no reason… for about a month. Then finally got a service start-stop message on dash. Aux battery was finally dead; replaced both batteries a few months ago (little guy was vamp’ing the bigger guy). Now back to “standard-normal” ESS operation again.

Good to know. So, the Aux is still probably on the way out... it's just being overly dramatic about it...

 

[TheBirdie72]

Good to know. So, the Aux is still probably on the way out... it's just being overly dramatic about it...

Haha yeah. More or less. Don’t just replace the aux batt, though. Replace them both, or replace the main & do the bypass.

 

[andy29847]

ESS troubles do not identify which battery is weak.

There are a lot of things that lockout the ESS. Was the "Avenger" light on when the ESS wasn't working?

 

[Bob Burd]

Also, you can cycle the EVIC display to get a message about ESS. Normally it says "Ready" a few minutes after startup, otherwise it displays a message about why it is not ready.

 

[Opus]

ESS troubles do not identify which battery is weak.

There are a lot of things that lockout the ESS. Was the "Avenger" light on when the ESS wasn't working?

Nope. When the ESS wasn't working there were no lights out of the ordinary. The Avenger light only came on when the ESS started working again today.

 

[Opus]

Haha yeah. More or less. Don’t just replace the aux batt, though. Replace them both, or replace the main & do the bypass.

Yeah, I fully expect at some point in the near future I'm going to go to start the Jeep and just get a "click". The way the batteries are dying, though, seems odd.

 

[gato]

There is a list of ~a dozen reasons as to why ASS would is not ready. You can cycle through the center display and see the reason. Could be "Battery Charging", "Engine Temperature", etc.

Sponsored