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 Descriptor
DTC P0480: Cooling Fan 1 Control Circuit MalfunctionDTC P0481: Cooling Fan 2 Control Circuit Malfunction
Diagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage |
|---|---|---|---|
Low Speed Cooling Fan Relay Control Circuit | P0480 | P0480 | P0480 |
Low Speed Cooling Fan Relay Coil Voltage Supply Circuit | P0480 | P0480 | P0480 |
High Speed Cooling Fan Relay Control Circuit | P0481 | P0481 | P0481 |
High Speed Cooling Fan Relay Coil Voltage Supply Circuit | P0481 | P0481 | P0481 |
Circuit/System Description
The engine control module (ECM) grounds the cooling fan relay control circuits through an internal solid state device called a driver. The primary function of the driver is to supply the ground for the component being controlled. Each driver has a fault line that is monitored by the ECM. When the ECM is commanding a component ON the voltage potential of the control circuit should be low, near 0 volts. When the ECM is commanding the control circuit to a component OFF the voltage potential of the circuit should be high near battery voltage. If the ECM detects that the actual state of the control circuit does not match the expected state, a DTC will set.
Conditions for Running the DTC
| • | The ignition is ON. |
| • | The system voltage is between 9-18 volts. |
Conditions for Setting the DTC
| • | An imcorrect voltage level has been detected on the cooling fan relay control circuit. |
| • | The condition must be present for a minimum of 30 seconds. |
Action Taken when the DTC Sets
DTCs P0480 and P0481 are type B DTCs.
Conditions for Clearing the MIL/DTC
DTCs P0480 and P0481 are type B DTCs.
Reference Information
Schematic Reference
Connector End View Reference
Electrical Information Reference
Scan Tool Reference
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 fan relay.
- Ignition ON, verify that a test lamp does not illuminate between the earth terminal and a known ground.
- Ignition ON, Connect a test lamp between the control circuit terminal and a known ground.
- Connect a test lamp between the Battery + terminal and a known ground.
- Connect a 30-A fusible link wire between the battery positive post and the fan voltage supply circuit terminal and verify fan activation.
- If all circuits test normal replace the affected relay.
| ⇒ | If the test lamp illuminates, test the control circuit for a short to voltage. |
Command the relay ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
| ⇒ | If the test lamp is always ON, test the relay control circuit for a short to voltage. If the circuit tests normal replace the ECM. |
| ⇒ | If the test lamp is always OFF, test the relay control circuit for a short to ground or an open/high resistance. If the circuit tests normal replace the ECM. |
| ⇒ | If the test lamp does not illuminates, test the Battery + for a short to ground or an open/high resistance. |
| ⇒ | 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. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Repair Verification
Ignition ON, command the relay ON and OFF with a scan tool. Feel or listen to verify that the relay turns ON and OFF with each command.
