P0480

P0480-COOLING FAN 1 CONTROL CIRCUIT/OPEN





For complete wiring diagrams refer to Diagrams/Electrical.


Theory of Operation

The cooling fan is a hydro-electric controlled device that is engine mounted. The ECM monitors various sensors to control fan speed. The cooling fan provides temperature control for engine coolant, engine charged air, A/C Freon and automatic transmission fluid. Fan speed increases as cooling requirements increase. Since the fan is mounted to the engine, fan speed is related to engine speed (RPM). The PCM sends a Pulse Width Modulated (PWM) signal to the cooling fan hub. As the PWM signal increases the fan hub which allows more fluid to drive the fan. When the fan is fully engaged it is capable of speeds about 10% greater than engine speed. The fan will rotate anytime the engine is running, even when the ECU is not send a PWM signal.

- When Monitored:

When the ignition is on.

- Set Condition:

When the control coil is electrically shorted or open.







Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.

Diagnostic Test


1. FAN CLUTCH





Disconnect the fan clutch harness connector.


NOTE: Check connectors - Clean/repair as necessary.

Measure the resistance between the Fan Clutch Driver circuit and the fan speed sensor return circuit on the fan clutch assembly.

Is the resistance less than 10 Ohms?

Yes

- Replace the fan clutch.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

No

- Go To 2

2. FAN CLUTCH





Disconnect the Fan Clutch harness connectors.


NOTE: Check connectors - Clean/repair as necessary.

Measure the resistance between the Fan Clutch Driver circuit and the fan clutch battery supply circuit on the fan clutch assembly.

Is the resistance less than 6 ohms or greater than 10 ohms?

Yes

- Replace the fan clutch.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

No

- Go To 3

3. FAN CLUTCH DRIVER CIRCUIT OPEN

Disconnect the ECM harness connectors.


NOTE: Check connectors - Clean/repair as necessary.

Measure the resistance of the fan clutch Fan Clutch Driver circuit between the ECM harness connector and the Fan Clutch harness connector.

Is the resistance less than 10 ohms?

Yes

- Go To 4

No

- Repair the open fan clutch river circuit.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

4. FAN CLUTCH DRIVER CIRCUIT SHORTED TO RETURN CIRCUIT





Measure the resistance between the Fan Clutch Driver circuit and the fan speed sensor return circuit at the sensor harness connector.

Is the resistance greater than 100K ohms?

Yes

- Go To 5

No

- Repair the Fan Clutch Driver circuit shorted to Return circuit.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

5. DRIVER CIRCUIT SHORTED TO BATTERY NEGATIVE





Measure the resistance between the fan clutch Fan Clutch Driver circuit and the battery negative.

Is the resistance greater than 100k Ohms?

Yes

- Go To 6

No

- Repair the Fan Clutch Driver circuit shorted to battery negative.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

6. ECM





Reconnect the ECM harness connectors.

Measure the resistance of the Fan Clutch Driver circuit between the fan clutch connector and battery negative.

Is the resistance greater than 100k Ohms?

Yes

- Refer to the INTERMITTENT CONDITION Diagnostic Procedure. Intermittent Condition

No

- replace the ECM.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test