Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
DTC Descriptors
DTC P0480: Cooling Fan Relay 1 Control CircuitDTC P0481: Cooling Fan Relay 2 Control Circuit
Diagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Low Speed Cooling Fan Relay Control Circuit for R1 Cool/Fan 1 Relay | P0480 | P0480 | P0480 | -- |
R1 Cool/Fan 1 Relay Coil Voltage Supply Circuit | P0480 | P0480 | P0480 | -- |
High Speed Cooling Fan Relay Control Circuit for R2 Cool/Fan Relay | P0481 | P0481 | P0481 | -- |
R2 Cool/Fan Relay Coil Voltage Supply Circuit | P0481 | P0481 | P0481 | -- |
High Speed Cooling Fan Relay Control Circuit for R7 Cool/Fan 2 Relay | P0481 | P0481 | P0481 | -- |
R7 Cool/Fan 2 Relay Coil Voltage Supply Circuit | P0480 | P0480 | P0480 | -- |
Circuit/System Description
The engine control module (ECM) commands the fans ON in high speed or low speed. In low speed, the fans are configured in series. In high speed, the fans are configured in parallel.
In low speed operation, the ECM applies ground to the coil side of the low speed relay, which is R1 cool/fan 1 relay. Voltage is applied directly to the left cooling fan through the switch side of the low speed relay. The right fan is connected in series to the left fan through the de-energized series/parallel relay, which is R7 cool/fan 2 relay, so that both fans operate at low speed.
In high speed operation, the ECM applies a ground to the coil side of the low speed relay, the series/parallel relay, and the high speed relay, which is relay R2 cool/fan relay. Voltage is applied directly to the right cooling fan through the switch side of the high speed relay. The left cooling fan obtains voltage through the low speed relay and ground through the series/parallel relay.
When the ECM is commanding a fan relay ON, the voltage of the control circuit should be low, near 0 volts. When the ECM is commanding a fan relay OFF, the voltage of the control circuit should be high, near battery voltage. If the ECM detects that the actual voltage of the relay control circuit is different than the expected voltage, DTC P0480 or P0481 will set and the affected ECM driver will be disabled.
Conditions for Running the DTC
| • | The ignition is ON. |
| • | The system voltage is between 9-18 volts. |
| • | The relay control circuit is transitioned from OFF to ON or ON to OFF. |
Conditions for Setting the DTC
P0480
The ECM detects an open circuit in the low speed cooling fan relay control circuit.
P0481
| • | The ECM detects an open circuit in the high speed cooling fan relay control circuit. |
| • | The above condition is present for 30 seconds. |
Action Taken When the DTC Sets
DTCs P0480 and P0481 are Type B DTCs.
Conditions for Clearing the DTC
DTCs P0480 and P0481 are Type B DTCs.
Reference Information
Schematic Reference
Connector End View Reference
Description and Operation
Engine Control Module Description
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Special Tools Required
J 43244 Relay Puller Pliers
Circuit/System Verification
Ignition ON, command each relay ON and OFF with a scan tool. Feel or listen to verify that each relay turns ON and OFF with each command.
Circuit/System Testing
- Ignition OFF, disconnect the series/parallel relay.
- Connect a 30A fused jumper between the normally-open switch contact terminals at the R7 cool/fan 2 relay connector in order to complete the fan ground circuit. Leave this jumper in place for the remainder of this procedure.
- Ignition OFF, disconnect the affected relay.
- Ignition ON, connect a test lamp between the positive terminal at the battery and the affected relay control circuit terminal.
- Command the affected relay ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
- Connect a 30A fused jumper between the positive voltage terminal at the battery and the fan voltage supply circuit terminal at the affected relay connector and verify fan activation.
- Ignition ON, connect a 30A fused jumper between the relay switch voltage supply circuit terminal and the fan voltage supply circuit terminal at the affected relay connector and verify fan activation.
- Ignition ON, verify that a test lamp illuminates between the affected relay coil voltage supply circuit terminal and ground.
- If all circuits and the ECM test normal, replace the affected relay.
| ⇒ | If the test lamp is always ON, test the relay control circuit for a short to ground. If the circuit tests normal, replace the ECM. |
| ⇒ | If the test lamp is always OFF, test the relay control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM. |
| ⇒ | If the fan does not activate, test the fan voltage supply circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the fan. |
| ⇒ | If the fan does not activate, test the affected relay switch voltage supply circuit for a short to ground or an open/high resistance. If the circuit tests normal and its fuse is open, test all connected components and replace as necessary. |
| ⇒ | If the test lamp does not illuminate, test the affected relay coil voltage supply circuit for a short to ground or an open/high resistance. If the circuit tests normal and its fuse is open, test all connected components and replace as necessary. |
Repair Verification
Ignition ON, command each relay ON and OFF with a scan tool. Feel or listen to verify that each relay turns ON and OFF with each command.
