Mine has not worked in like 8 months. I hate the feature, but it definitely indicates something is broken. I have not found the time to take it to the dealer though. I guess in the next couple weeks.Sorry to bump such an old thread, but the ESS system is definitely weird in the Jeep.
My daily commute typically involves 10mins of motorway driving and 20mins of city driving. So I would have thought the battery would be well charged for ESS to be active? Instead it very rarely activates. So far I have gone 2 weeks without ESS working.