Electronic Control Module (ECM)

When the electronic control module (ECM) detects that the ignition is being turned ON, the ECM waits for a release message from the immobilizer control unit. If a release message is not received within a specified time, the ECM disables the engine. The engine is also disabled it the identification (ID) code transmitted by the immobilizer control unit does not match the code stored in the ECM's memory. Immobilization remains in effect until the ignition is turned OFF or until battery power is removed.
To prevent the vehicle from being driven, the ECM applies the following strategy:
- The ignition module is put in a bypass mode.
- The ECM will not create an electronic spark timing (EST) output, so no spark will be generated by the ignition coil.
- The ECM will not enable the fuel pump.
- The ECM will not enable the fuel injectors.
- The ECM sets diagnostic trouble code (DTC) 58.
Serial data communication is transmitted on a single wire between the immobilizer control unit and the ECM. During diagnostic procedures or ID code changing, a scan tool is added to the communication system.
An ECM with an immobilizer control unit is not exchangeable with an ECM that does not have an immobilizer control unit.