No Communication

ECM-720A IMMOBILIZER COMMUNICATION
FAULTY COMMUNICATION

Reading off the status of the diagnostic trouble code (DTC):



Note! When Reading the diagnostic trouble code (DTC) status, other stored diagnostic trouble codes (DTCs) and their status will be listed.

- Start the engine. Let it idle for at least 15 seconds.
- Read the diagnostic trouble code (DTC) status. Check the status of the relevant diagnostic trouble code (DTC).

Was the status of the relevant diagnostic trouble code (DTC) permanent?
Yes - Skip to "Other Diagnostic Trouble Codes (DTCs)"
No - Continue below.


Intermittent fault
The engine control module (ECM) has previously detected a fault in the communication between the immobilizer and engine control module (ECM).

Hint: This diagnostic trouble code (DTC) is stored when the car is left standing with the ignition on for too long. The engine control module (ECM) then requires a new approval code from the immobilizer. When the engine is next started, the immobilizer will be in the diagnostic mode. The immobilizer goes into the diagnostic mode if there has been diagnostic communication between the immobilizer control module and the engine control module (ECM) and the engine is started without the ignition being switched off first.

Visually check the immobilizer terminals and connections according to [1][2]Checking Wiring and Terminals. Intermittent Faults

Check the signal cable between engine control module (ECM) terminal # B22 (# B32) and immobilizer terminal # 4 (# 50) for an intermittent open-circuit according to [1][2]Checking Wiring and Terminals. Intermittent Faults Check for an intermittent short-circuit to ground according to [1][2]Checking Wiring and Terminals. Intermittent Faults Check for an intermittent short-circuit to supply voltage according to [1][2]Checking Wiring and Terminals. Intermittent Faults

Remedy as necessary.


Fault-tracing information
If the fault is intermittent, do not verify fault-tracing if the fault does not recur.
--Testing Complete--


Other Diagnostic Trouble Codes (DTCs)



Read the diagnostic trouble codes (DTCs) in the immobilizer control module.

If there is a diagnostic trouble code (DTC) stored in the immobilizer control module, fault trace accordingly.

Were there any diagnostic trouble codes (DTCs) stored in the immobilizer control module?
Yes - Test Complete.
No - Continue below.


Replacing and programming the engine control module (ECM)



- The control module has registered an internal fault.

Caution! A new control module is delivered without software. The control module must be programmed in order to function after replacement.

For further information about programming and replacing the control module, Engine Control Module (ECM), Replacing


Fault-tracing information
Fault-tracing is not followed by verification for this fault.