Engine Control Module: Testing and Inspection

Engine Control Module Voltage Supply, Checking

Special tools, testers and auxiliary items required

• Multimeter.

• wiring diagrams.

Test requirements

• Fuse (SD3) OK.

• Fuse (SC36) OK.

• Motronic Engine Control Module (ECM) Power Supply Relay (J271) OK.

• Power Supply Relay (terminal 50) (J682) OK.

• The Ground (GND) connections at the engine and transmission OK.

• The battery voltage at least 12.5 V.

• The generator OK.

Start diagnosis

If the manufacturers test box is being used. Perform the following step.

- Install the test box.

If the manufacturers test box is not being used. Perform the following step.

- Remove the Engine Control Module (ECM) (J623). Refer to => [ Engine Control Module, Replacing ] Engine Control Module, Replacing.

Checking voltage supply

- Using a Multimeter, check the following wiring connection for voltage.






Specified value: 12.5 V

If the specified value was not obtained:

- Check the Engine Control Module (ECM) (J623) electrical harness connector terminal T81/62 to the Battery (A) (+) for an open circuit or short to Ground (GND).

- Check the electrical harness connectors for damage, corrosion, loose or broken terminals.

- If necessary, repair the wiring connection.

If no malfunctions are found in the wiring:

Checking switched voltage supply

- Switch the ignition on.

- Using a Multimeter, check the following wiring connection for voltage.






Specified value: 12.5. battery voltage.

- Switch the ignition off.

If the specified value was not obtained:

- Check the Engine Control Module (ECM) (J623) electrical harness connector terminal T81/28 to the Voltage Regulator (VR) (C1) terminal DF for an open circuit or a short to Ground (GND).

- Check the electrical harness connector for damage, corrosion, loose or broken terminals.

- If necessary, repair the wiring connection.

If no malfunctions are found in the wiring:

- Switch the ignition on.

- Using a Multimeter, check the following wiring connection for voltage.






Specified value: 12.5 V

- Switch the ignition off.

If the specified value was not obtained:

- Check the Engine Control Module (ECM) (J623) electrical harness connector terminal T81/21 to Battery (A) (+) connection 1 for an open circuit or short to Ground (GND).

- Check the electrical harness connectors for damage, corrosion, loose or broken terminals.

- If necessary, repair the wiring connection.

If no malfunctions are found in the wiring:

Checking Ground (GND)

- Using a Multimeter, check the following wiring connections for resistance.






Specified value: 1.5 ohms.

If any of the specified values are not obtained:

- Check the Engine Control Module (ECM) (J623) electrical harness connector terminals to the following Ground (GND) locations for an open circuit or a short to Battery (+).






- Check the electrical harness connector for damage, corrosion, loose or broken terminals.

- If necessary, repair the wiring connection.

If no malfunctions are found in the wiring and the voltage supply was OK:

- Perform a road test to verify any electrical repairs.

If the fault does not return:

Repair complete, Generate readiness code. Refer to => [ Readiness Code ] Engine.

- End diagnosis.

If the fault does return and no malfunction is detected in the wiring and the voltage supply was OK:

- Replace the Engine Control Module (ECM) (J623). Refer to => [ Engine Control Module, Replacing ] Engine Control Module, Replacing.

- Assembly is performed in the reverse of the removal.

Final procedures

After the repair work, the following work steps must be performed in the following sequence:

1. Check the DTC memory. Refer to => [ Diagnostic Mode 03 - Read DTC Memory ] Diagnostic Mode 03 - Read DTC Memory.

2. If necessary, erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Mode 04 - Erase DTC Memory.

3. If the DTC memory was erased, generate readiness code. Refer to => [ Readiness Code ] Engine.

End diagnosis.