Supply Monitoring
WARNING: This page is about a different car, the 2005 Jaguar XJR, 2005 Jaguar XJ8, 2004 Jaguar XJR, and 2004 Jaguar XJ8. However, it is still accessible from the selected car via links, so may be relevant.
If the battery voltage is either too great or too low, the TCM will detect a fault condition. For the TCM to be able to identify this fault, the engine must be running and the transmission fluid temperature sensor must be functioning correctly.