Circuit Description
| • | DTC P0480 is for the cooling fan 1 control circuit. |
| • | DTC P0481 is for the cooling fan 2 control circuit. |
Battery positive voltage is supplied to the cooling fan control module from the COOL FAN #1 and COOL FAN #2 fuses. The engine control module (ECM) controls the relays in the cooling fan control module by grounding the cooling fan 1 and cooling fan 2 control circuits.
When the ECM is commanding a fan control circuit on, the voltage potential of the control circuit should be low, near 0 volts. When the ECM is not commanding the control circuit on, the voltage potential of the circuit should be high, near battery voltage. If the fault detection circuit senses a voltage other than what is expected, the DTC will set.
The ECM will monitor the control circuit for the following:
| • | A short to ground |
| • | A short to voltage |
| • | An open circuit |
| • | An internally shorted or excessively low resistance cooling fan control module |
When the ECM detects any of the above conditions, the DTC will set and the affected driver will be disabled.
DTC Descriptors
This diagnostic procedure supports the following DTCs:
| • | DTC P0480 Cooling Fan Relay 1 Control Circuit |
| • | DTC P0481 Cooling Fan Relay 2 Control Circuit |
Conditions for Running the DTC
| • | The ignition is ON. |
| • | System voltage is between 9-18 volts. |
| • | The control circuit is transitioned from OFF to ON or ON to OFF. |
Conditions for Setting the DTC
| • | The ECM detects an open, a short to ground or a short to voltage on the cooling fan control circuit. |
| • | The above conditions are present for at least 30 seconds. |
Action Taken When the DTC Sets
| • | The ECM will illuminate the malfunction indicator lamp (MIL) during the second consecutive trip in which the diagnostic test has been run and failed. |
| • | The ECM will store conditions which were present when the DTC set as Freeze Frame and Failure Records data. |
Conditions for Clearing the MIL/DTC
| • | The ECM will turn OFF the MIL during the third consecutive trip in which the diagnostic has been run and passed. |
| • | The History DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction. |
| • | The DTC can be cleared by using the scan tool. |
Diagnostic Aids
| • | If the condition is not present, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. |
| • | Review the Freeze Frame/Failure Records vehicle mileage since the diagnostic test last failed. This may help determine how often the condition that caused the DTC to be set occurs. |
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Engine Cooling Schematics Connector End View Reference: Cooling System Connector End Views | |||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
2 |
Test the appropriate control circuit of the cooling fan control module for a short to ground, short to voltage, high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 11 | Go to Step 3 |
3 |
Does the test lamp turn ON and OFF with each command? | Go to Step 4 | Go to Step 8 |
4 | Test the battery positive voltage circuits of the cooling fan control module for a short to ground, open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 11 | Go to Step 5 |
5 | Test the ignition 3 voltage supply circuit of the cooling fan control module for a short to ground, open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 11 | Go to Step 6 |
6 | Test the ground circuit of the cooling fan control module for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 11 | Go to Step 7 |
7 | Inspect for poor connections at the cooling fan control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 11 | Go to Step 9 |
8 | Inspect for poor connections at the harness connector of the ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 11 | Go to Step 10 |
9 | Replace the cooling fan control module. Refer to Cooling Fan Control Module Replacement in Engine Cooling. Did you complete the replacement? | Go to Step 11 | -- |
10 | Replace the PCM. Refer to Control Module References in Computer/Integrating Systems for Replacement, Setup, and Programming. Did you complete the replacement? | Go to Step 11 | -- |
11 |
Does the DTC reset? | Go to Step 2 | System OK |
