Diagnostic trouble code (DTC) information

IMM-321 Communication with the engine control module (ECM)

Condition

Fig 1: Immobilizer Control Module And Engine Control Module (ECM) Communication Diagram

Courtesy of VOLVO CARS OF NORTH AMERICA.

This diagnostic trouble code (DTC) only applies to cars with gasoline engines and EMS 2000 engine management systems.

During the first two seconds after the ignition is switched on, the immobilizer control module checks the communication link between the immobilizer control module and the engine control module (ECM) for an open-circuit or a short-circuit to supply voltage. Diagnostic trouble code (DTC) IMM-321 is stored if the immobilizer control module is unable to detect communication with the engine control module (ECM) and there is no short-circuit to ground.

If there is no power supply (+15 and / or +30) to the engine control module (ECM) this will indirectly cause diagnostic trouble code (DTC) IMM-321 to be stored. This is because communication between the immobilizer control module and the engine control module (ECM) cannot be established.

Possible Source

CAUTION:

This diagnostic trouble code can also be generated due to short intermittent open circuits in the ignition. This is solved according to technical journal TJ 4920. If TJ 4920 is introduced, the problem cause can be searched for in cables and relay according to wiring diagram in TJ 4920.

Short-circuit to supply voltage in the cable between engine control module (ECM) #B56 and immobilizer control module #4 when starting.
Open-circuit in the cable between engine control module (ECM) #B56 and immobilizer control module #4 during start.
Contact resistance in the wiring terminals between immobilizer control module #4 and engine control module (ECM) #B56.
Intermittent open-circuit in the power supply to immobilizer control module #5 while driving, for example there are loose connections in the +15 supply.
Intermittent open-circuit in the power supply to immobilizer control module #6 while driving, for example there are loose connections in the +30 supply.
Intermittent open-circuit in the ground terminal for immobilizer control module #8 while driving.
Ignition switched on when the engine control module (ECM) is disconnected.
Fault in the engine control module (ECM)
Incorrect engine control module (ECM) installed.
Open-circuit in the power supply to the engine control module (ECM).

Fault symptom[s]

The indicator lamp on the combined instrument panel lights.
The engine starts but stops immediately.