Engine Control Module: Testing and Inspection

Voltage Supply, Checking

Special tools, testers and auxiliary items required

• Multimeter.

• Wiring diagram.

Test requirements

• The Engine Control Module (ECM) (J623) fuses OK.

• Battery voltage at least 12.5 volts.

• All electrical consumers such as, lights and rear window defroster, switched off.

• Vehicles with automatic transmission, selector lever in position "P" or "N".

• A/C switched off.

• Ground (GND) connections between engine/transmission/chassis OK.

• Ignition switched off.

Test procedure

- Perform a preliminary check to verify the customers complaint. Refer to => [ Preliminary Check ] Preliminary Check

Start diagnosis

- Remove the Engine Control Module (ECM) Power Supply Relay (J271).

Checking voltage

- Using a Multimeter, check the Engine Control Module (ECM) Power Supply Relay (J271) socket 4/85 to Ground (GND).

Specified value: battery voltage.

If the specified value was not obtained:

- Check the wiring connections from the Battery to the Engine Control Module (ECM) Power Supply Relay (J271) socket 3/86 for an open circuit or a short circuit.

- Check the wiring connections for damage, corrosion, lose or broken terminals.

- If necessary, repair the faulty wiring connection.

If the specified value was obtained:

- Switch the ignition on.

- Using a Multimeter, check the Engine Control Module (ECM) Power Supply Relay (J271) socket 4/85 to Ground (GND).

Specified value: battery voltage.

If the specified value was obtained:

Checking wiring

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

- Install the Test Box 105 Pin (VAG1598/31).

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 J623, Replacing ] Engine Control Module J623, Replacing.

- Using a Multimeter, check the Engine Control Module (ECM) Power Supply Relay (J271) socket 4/85 to the Engine Control Module (ECM) (J623) electrical harness connector T121 terminal 65 for resistance.






Specified value: 2.0 ohms Max.

If the specification was not obtained:

- Check the wiring for a short circuit to each other, Battery (+), and Ground (GND).

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

- If necessary, repair the faulty wiring connection.

If no malfunction is found in the wiring:

Checking activation

- Switch the ignition on.

- Using a Multimeter, check the Engine Control Module (ECM) Power Supply Relay (J271) socket 4/85 to the Engine Control Module (ECM) (J623) electrical harness connector T121 terminal 65 for voltage.






- Switch the ignition off.

Specified value: 0.5 V Max.

If the specified value was obtained:

- Replace the Engine Control Module (ECM) Power Supply Relay (J271).

If the specified value was not obtained:

- Check the wiring connection for an open circuit, short circuit to Battery (+) or Ground (GND).

- Check the wiring connection for damage, corrosion, lose or broken terminals.

- If necessary, repair the faulty wiring connection.

If no malfunction is found in the wiring and voltage supply was OK:

- Erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Mode 04 - Erase DTC Memory

- Perform a road test to verify repair.

If the DTC does not return:

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

- End diagnosis.

If the DTC 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 J623, Replacing ] Engine Control Module J623, Replacing.

- Assembly is performed in the reverse of the removal.

Final procedures

After 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 ] Readiness Code Description.

- End of diagnosis.