Diagnostic trouble code (DTC) information

Condition

Fig 1: Identifying Engine Control Module

Courtesy of VOLVO CARS OF NORTH AMERICA.

The engine control module (ECM) interprets the following as faults: If the engine control module (ECM) does not communicate with the immobilizer-function (in the central electronic module (CEM)) within 2 seconds of the ignition being switched on. If there is "no communication". If the +15-supply between the ignition switch and the engine control module (ECM) is switched on and off while driving. If there is a "faulty signal". If a "faulty VIN code" is sent from the immobilizer function. Diagnostic trouble code ECM-720A is stored if any of these faults occurs.

Substitute Value

None.

Possible Source

Faulty communication:

the ignition has been switched on and off more than three times while driving.

No communication:

faulty key (transponder read off or not programmed)
open-circuit or interference in the communication cable between the central electronic module (CEM) and the engine control module (ECM)
defective central electronic module (CEM)
defective central electronic module (CEM).

Incorrect VIN code:

defective central electronic module (CEM)
defective central electronic module (CEM)
defective engine control module (ECM)
faulty engine control module (ECM).

Fault symptom[s]

the engine starts but stops immediately.