I had this problem too! My ESS light was on right after I picked up from dealer, then we started hearing the fan coming on, and being noisy. The dealer I took it to (not the one I purchased from) updated a flash or something like that. Hope this helps you!
Sure is discouraging to see all these unresolved ESS issues. Like others, my ESS light was on when I picked up from the dealer. I called the dealer to see if it was safe to drive, service there at the dealer (where I purchased, in Houston) said it was most likely battery. Fast forward two...