Auto Start/Stop Not Working....Fix it?

[Spacenut]

My used 2018 rubicon s/s never worked and I'm not sure why. I have jscan but never touched that setting and it looks like the Aux battery is still hooked up. Glad it doesn't work so I have never looked into it.

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[AndySpill]

What year did they start putting aux batteries in Jeeps? I have a 2018 JL and want to know if I will be seeing this.

Your 2018 JL (not a 2018 JK) was the first year in which this factory dual battery design was implemented. You have it.

Sadly though it gets worse for you.

Some of the early 2018s were designed that if the Auxiliary battery lacked adequate charge the vehicle would not even attempt to cold crank.

This behavior, if present in your 2018, is addressed by having a dealer's service department apply TSB 18-092-19. This will allow the vehicle to attempt a cold crank against solely the main battery on the second attempt and all attempts thereafter, if the Auxiliary battery is seen as dead on the first crank try. Later model 2018s and beyond, of the dual AGM battery JL seem to have this newer crank behavior that the TSB provides, built in.

The ESS off light in the dash will turn on and all subsequent cranks should happen on the first attempt. That ESS off light on the dash will remain illuminated, using only the main battery until the sooner of the Auxiliary battery is replaced or bypassed.

Links for how to bypass your Auxiliary battery, which I feel you should only do if you've committed to not running ESS events, are available upon request.