@MauiMom, Thank you for the follow-up. I only have one comment. Always disconnect the NEGATIVE post first on a battery. For safety’s sake. All cars today are negative grounded, so the metal body and metal on the engine are directly connected to the negative post of the battery. with the negative connected, any accidental contact with a metal wrench on the positive post with anything metal on the car will cause a dead short with the battery. 3rd degree burns are common. Exploding batteries are a real possibility. Batteries can discharge enough energy in a dead short to weld steel. By disconnecting the negative, this eliminates the danger. And is just as effective as disconnecting the positive for resetting the electronics. Also, since the rental service will pay, do the fluid changes, not flushes. Cars love fresh fluids.
If the car sharing service changes the renters credit card for everything, you should have the car cleaned, change the oil, get diagnostic tests, and charge it all to the renter’s card. The gas cap goes on the bill as well, and since this was a business transaction, you should charge for your time. As a businesswoman, you spent a lot of time running around town getting parts and discussing the issue with the dealer and your regular mechanic. Sit down now and itemize the things you did and how much time it took. All your mileage should be charged too. I don’t know what you pay for gas, but I’ll bet it is a lot more than we do on the mainland. Itemize all your expenses and submit the bill. You deserve to be made whole, and a several hundred dollar surprise might knock some sense into the boob that rented your car.