P0483

P0483-COOLING FAN SPEED





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 ECM 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:

While the engine is running.

- Set Condition:

The actual fan speed is less than 50 RPM or more than 6000 RPM.







Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.

Diagnostic Test


1. OTHER DTC'S PRESENT

With the scan tool, read DTCs.

Is DTC P0480 present?

Yes

- Repair other DTC's first.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

No

- Go To 2

2. FAN CLUTCH SHORTED

Disconnect the wiring harness from the fan clutch assembly.


NOTE: Check connectors - Clean/repair as necessary.

Measure the resistance between the (N27) signal circuit in the fan clutch assembly and the (K161) return circuit in the fan clutch assembly.

Is the resistance less than 10 Ohms?

Yes

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

No

- Go To 3

3. FAN CLUTCH ASSEMBLY SHORTED TO GROUND

Measure the resistance between the (N27) signal circuit in the fan clutch assembly and battery negative.

Is the resistance less than 10 Ohms?

Yes

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

No

- Go To 4

4. (N27) SIGNAL CIRCUIT SHORT TO 5-VOLT SUPPLY CIRCUIT





Disconnect the Fan clutch connector.


NOTE: Check connectors - Clean/repair as necessary.

Measure the resistance between the (N27) signal circuit in the fan clutch assembly and the battery 5-volt supply circuit in the fan clutch assembly.

Is the resistance less than 10 Ohms?

Yes

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

No

- Go To 5

5. (N27) SIGNAL CIRCUIT OPEN FROM ECM TO FAN CLUTCH ASSEMBLY





Disconnect the ECM harness connectors.

Check connectors - Clean/repair as necessary.

Measure the resistance of the (N27) signal circuit between the ECM harness connector and the fan clutch assembly harness connector.

Is the resistance less than 10 Ohms?

Yes

- Go To6

No

- Repair the open circuit from the ECM harness connector to the Fan clutch harness connector.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

6. (K855) 5-VOLT SUPPLY CIRCUIT OPEN FROM ECM HARNESS CONNECTOR TO FAN CLUTCH HARNESS





Measure the resistance of the (K855) 5-volt supply circuit between the ECM harness connector and the fan clutch assembly harness connector.

Is the resistance less than 10 Ohms?

Yes

- Go To 7

No

- Repair the open (K855) 5-volt circuit from ECM harness connector to Fan clutch connector.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

7. (N27) SIGNAL CIRCUIT SHORTED TO RETURN IN THE HARNESS





Measure the resistance between the (N27) signal circuit in the fan clutch assembly harness connector and the return circuit in the fan clutch assembly harness connector.

Is the resistance less than 10 Ohms?

Yes

- Repair the shorted (K161) circuit.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

No

- Go To8

8. (N27) SIGNAL CIRCUIT SHORTED TO VOLTAGE





Measure the voltage between the signal circuit in the fan clutch assembly harness connector and battery negative.

Is the voltage greater than 1 volt?

Yes

- Repair the (N27) signal circuit shorted to voltage.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

No

- Go To 9

9. (N27) SIGNAL CIRCUIT IN ECM SHORTED TO GROUND INSIDE ECM





Reconnect the ECM harness connectors.

Measure the resistance between the (N27) signal circuit in the fan clutch assembly harness connector and battery negative.

Is the resistance less than 10 Ohms?

Yes

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

No

- Go To10

10. (N27) SIGNAL CIRCUIT SHORTED TO VOLTAGE IN THE ECM





Reconnect the fan harness connector.

Turn the ignition on.

While back probing the fan connector measure the voltage between the fan speed (N27) signal circuit in the fan clutch assembly harness connector and battery negative while manually rotating the fan blade.

Did voltage go from less than 0.7 volts to 4.5 to 5.5 volts?

Yes

- Repair the Fan Speed Signal circuit in the engine harness.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

No

- Go To 11

11. (K855) 5-VOLT SUPPLY CIRCUIT IN ECM





Turn the ignition on.

Measure the voltage between the (K855) 5-volt supply circuit in the fan clutch assembly harness connector and battery negative.

Is the voltage between 4.5 and 5.5 volts?

Yes

- Refer to the INTERMITTENT CONDITION Diagnostic Procedure. Intermittent Condition

No

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