Cooling Fan Control Circuit, Checking

Diagnostic Procedures

Cooling Fan Control Circuit, Checking

Special tools, testers and auxiliary items required

• Multimeter.

• Test lamp

• Wiring diagram.

Test requirements

• The Cooling Fan Module fuse S5 is OK.

• Battery voltage at least 12.5 V.

• All electrical consumers switched off.

• A/C switched off.

• The ignition switched OFF.

Test procedure

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

Start diagnosis

- Disconnect the Cooling Fan Control Module electrical harness connector.

Checking voltage supply

Switch the ignition ON.

- Using a multimeter, check the Cooling Fan Control Module harness connector terminal 1 to ground for voltage.

- Using a multimeter, check the Cooling Fan Control Module harness connector terminal 2 to ground for voltage.

Specified value for both terminals: Battery voltage.

Switch the ignition OFF.

If the specified value was Not obtained:

- Check the wiring from the Cooling Fan Control Module harness connector terminal 1 to fuse S-163 or terminal 2 to fuse S-5 for high resistance, a short circuit to Ground, or an open circuit. Refer to the Wiring Diagram.

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

- If necessary, repair the wiring connection and replace any blown fuse.

If the specified value was obtained:

- Connect a test lamp to Battery positive. Connect the other end to terminal 4 of the Cooling Fan Control Module harness connector.

Specified value: Test lamp is ON.

If the specified value was Not obtained:

- Check the wiring for an open or high resistance.

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

- If necessary, repair the faulty wiring connection.

If the specified value was obtained:

Checking wiring

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 Motronic Engine Control Module (ECM) ( J220). Refer to the Repair Information.

- Using a multimeter, check the Cooling Fan Control Module (-N112-) harness connector terminal 3 to the Motronic Engine Control Module (ECM) (J220) electrical harness connector T121 for high resistance or an open circuit.





Specified value: 1.5 ohms Max.

If the specified value was Not obtained:

- Check the wiring for an open, high resistance or short to ground.

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

- If necessary, repair the faulty wiring connection.

If no malfunction is detected in the wiring:

- Replace the Motronic Engine Control Module (ECM) (J220). Refer to the Repair Information.

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 Modes 01 - 09.

2. If necessary, erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09.

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