I have a 2019 Cherokee Latitude. The ESS states not ready if the AC/Heater are cooling or heating the cabin. Is this normal?

 

Nope. Not normal.

If you start having other weird errors like the wipers not working or error messages on the dash, suspect the battery or the battery connections. The various computers, such as the body computer, are sensitive to voltage issues. The body computer in particular needs the fuse pulled to get it to reboot. In my case, it started with the wipers stuck on which cleared after pulling the fuse for the body computer and reinserting. Then it started with ESS warnings and power steering warnings the next day. Cleaned and tightened the battery cables and it's been fine ever since.

 

Thanks, I cleaned all battery connections and removed and replaced the body computer fuse. For the first time in a long time my systems are working correctly

 

Cool!

I think we need to make this a sticky. There have been a lot of posts about this being the cure, sometimes after the shop couldn't trace down an intermittent problem and starts replacing expensive parts. Or replacing the battery fixed it, when the problem was really the connections that got cleaned up at the same time.

It's one of those things that isn't obvious because it looks like the battery and charging system are fine, and it still cranks and fires quick enough that you might not even notice it cranking a little slower. Whats happening is the voltage drop across the dirty terminals gets bad enough during cranking that the computers freak out from the low voltage. I was seeing 3-volts loss across the positive battery connector until I cleaned and re-tightened it. The body computer is always powered unlike some of the other control modules, so you actually need to disconnect power to get it to reboot.

 

I believe if the car has just been started it needs to run for a bit so that the AC cools or the water temp gets
warm enough to heat. So, the motor doesn't stop every few minutes on your drive.
Mine does some weird stuff on occasion. That's why I don't use "ESS"!
That is "electronic stop start" we are talking about, right?
I also think, if the voltage is low, it won't let it turn on until the battery charges for a little bit.
That is what happened to me.
You can have a low battery, and the computer shuts off the starting system and the car
will have lights but won't even attempt to turn over the engine.
Too much computer crap if you ask me!