Antitheft and Alarm Systems

Circuit Description
When the ignition is turned ON, the key is tested by the immobilizer anti-theft system. While the key code is being read by the immobilizer control unit, the engine can start and run 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 immobilizer control unit. If a valid key is detected, the immobilizer control unit sends a serial data release message to the electronic control module (ECM). Included in the release message is an identification (ID) cede which assures that neither the immobilizer control unit nor the ECM have been substituted to defeat the system. If the ECM receives an invalid release message, the ECM performs the following actions:
- Disables the fuel injector circuit.
- Disables the fuel pump circuit.
- Disables the ignition coil.

DTC 53 Will Set When
- The ECM does not receive the signal from the immobilizer control module within .582 second when the vehicle is stationary or within 1 .5 seconds when the vehicle is moving.
- The ECM receives an incorrect release message from the immobilizer control unit more than five times.
The above conditions are maintained until the ignition is switched OFF.

Step 1 - 6:

DTC 53 Will Clear When
- The ignition switch is turned OFF or the scan tool CLEAR CODES command is issued.