Circuit Description

When the ignition switch is turned to ON position, the ignition key is tested by the theft deterrent system. While the ignition key code is read by the theft deterrent control module, the engine can start to run for 2 seconds with any key that will turn the lock cylinder. The key code is read and compared with key codes that have been stored in the memory of the theft deterrent control module. If a valid key is detected, the theft deterrent control module sends a serial data release message to the engine control module (ECM) which will allow the engine to continue to run. Included in the release message is an identification (ID) code which assures that neither the theft deterrent control module or the ECM have been substituted to defeat the system. If the ECM receives an invalid release message or can not communicate with the theft deterrent control module, it will disable the fuel system.

If the ECM receives an invalid release message from the theft deterrent control module, this DTC sets.