2003 Jaguar S-Type engine

The passive anti-theft system (PATS) prevents the vehicle from being driven away by an unauthorized persons. The PATS system consists of encrypted electronically coded keys, a transceiver, instrument cluster (IC), and an engine control module (ECM). When the key is inserted into the ignition barrel, the ECM uses a decoding process via the transceiver to validate the key transponder code. If the code matches one that is stored and the key is then turned to the run position, the ECM will enable the fuel injectors, ignition coils, fuel pump drive and starter.
If the key is invalid the control function will send a theft status message to the ECM, which will disable, which will disable the vehicle from starting. If the correct key is used without a transponder or used with a transponder with an incorrect code, the vehicle will be inhibited from starting. This will prevent vehicle theft even if a duplicate key is cut.
If a valid key is read by the instrument cluster, the front electronic module (FEM) and the rear electronic module (REM) will allow the steering column lock actuator to unlock.
A PATS indicator LED (located on the instrument panel) provides the driver with the status of the PATS system. When the ignition is switched to the run position, the PATS indicator LED will illuminate for three seconds and extinguish. If there is a fault with the PATS system after 60 seconds of continuous flashing, the PATS indicator LED will flash an error code.