Intermittent no start on 2018 Rubicon JL

[Martiwnc]

I have seen many posts about intermittent no start on 2018 models. I have not seen any definitive answers or fixes.
I recently purchased a pre owned 2018 Rubicon JL manual transmission with 22,000 miles. I have been unable to drive because of intermittent no start issue. It cranks all lights come on but doesn’t start. Dealer can’t find a cause and no error codes. Has anyone found resolution? Sounds like Jeep put out a bunch of lemons in 2018.

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[aldo98229]

Welcome to the forum!

I had that happen right before I replaced both batteries. Hasn't happened again since.

Modern electronics are weird in that you don't get that cranking sound we used to get of a car struggling with a drained battery. These days you just get nothing, zero, zilch.

Good luck!

 

[Gee-pah]

Marti @Martiwnc to Aldo's point @aldo98229, did the dealer load test each battery independently?

So we're clear on language, this involves taking not a battery voltage tester, but a load tester to each battery, first disconnecting each battery from the other, and testing each battery's ability to both delivery and accept charge independently.

In the 3.6L engine models those batteries are connected in parallel at all times but an instant before crank, and during ESS events. Accordingly, one can neither take a battery tester or load tester to the terminals of either battery or they will get a composite test of both batteries. First, the batteries must be separated and the test done on each battery alone.

Battery problems need to be ruled out--although in your case they may not be the (only) problem. I say this because a 2018 3.6L, as from the factory, will not even attempt the (failed) crank I hear on your attachment, if the ESS battery is dead--not unless it has been updated with TSB 18-092-19 from a dealer.

This upgrade will allow the 2018 3.6L to behave like 2019's and later, in which a dead ESS battery will allow the operator, upon a second crank attempt, to crank off the main battery.

And while your dealer should be able to do this blindfolded, separating the batteries can be done by temporarily removing the cables on the main battery's negative post. Load testing thereafter against the main battery's posts will test only the main battery, and moving the negative of the load tester to the temporarily dangling wire group will test the ESS battery only--yes, even with the positive of the load tester still attached to the main battery's positive post.

Make sure to reattach all cables after this test.

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