Diagnostic Trouble Code (DTC) Information ECM-720A
Condition
The engine control module (ECM) contains a code for the immobilizer which is unique to each car. The unique code is checked so that it corresponds to the central electronic module (CEM) and the engine control module (ECM). The electronic immobilizer has another criterion that must be met before it allows the engine to start. A check is performed via CAN communication to ensure that the hardware series number on the brake control module (BCM) corresponds to the number stored in the engine control module (ECM).
The hardware series number is automatically stored when downloading software to the engine control module (ECM). If the hardware series number corresponds to the engine control module (ECM) and the brake control module (BCM), the electronic immobilizer will allow the engine to start. The diagnostic trouble code (DTC) is stored (signal missing) if the engine control module (ECM) registers that there is a fault in the CAN communication between the engine control module (ECM) and the brake control module (BCM). The diagnostic trouble code (DTC) is stored (comparison fault) if the hardware series number in the brake control module (BCM) does not correspond to the number stored in the engine control module (ECM). The diagnostic trouble code (DTC) is stored (communication fault) if the engine control module (ECM) registers a fault related to the immobilizer function in the central electronic module (CEM).
The diagnostic trouble code (DTC) can be diagnosed when the ignition is switched on.
Substitute Value
None.
Possible Source
Signal missing
- Fault trace the brake control module (BCM).
Comparison fault
- The programmed hardware series number in the engine control module (ECM) does not correspond to the relevant hardware series number in the brake control module (BCM).
Communication fault
- Fault trace the central electronic module (CEM)
- The engine control module (ECM) or central electronic module (CEM) has been replaced and contains incorrect software.
Fault symptom[s]
- The starter motor turns but the engine does not start.