Radiator Cooling Fan: Testing and Inspection
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 ] Monitors, Trips, Drive Cycles and Readiness Codes.