Long story short, had a sensor replaced due to the battery finally going out. The car was fine for a couple of weeks, but now I get the dreaded warning. I took it back to the shop to have them check all the tire pressures and they are fine. They checked all 4 sensors and they are working fine. What else could it be? I read on a Jaguar forum that sometimes our system needs a reflash at the dealer. Is this true?