Circuit Description
The powertrain control module (PCM) sends a pulse width modulation (PWM) signal of 0-12 volts via the cooling fan clutch control circuit to the cooling fan relay. The PCM monitors the cooling fan clutch control circuit during vehicle operation. When the cooling fan is commanded on by the PCM, the control circuit is at a low voltage. When the cooling fan is commanded off, the control circuit is near battery voltage. The PCM uses this PWM to control the position of the oil control valve located inside the cooling fan clutch. If during operation, the PCM detects an improper circuit condition on the cooling fan clutch control circuit DTC P0480 will set.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0480 Cooling Fan Relay 1 Control Circuit
Conditions for Running the DTC
| • | The engine speed is greater than 400 RPM. |
| • | The ignition voltage is greater than 10 volts and less than 18 volts. |
Conditions for Setting the DTC
| • | The PCM detects that the commanded state of the relay and the actual state of the control circuit do not match. |
| • | The above condition is present for at least 5 seconds. |
Action Taken When the DTC Sets
| • | The PCM will illuminate the malfunction indicator lamp (MIL) during the second consecutive trip in which the diagnostic test has been run and failed. |
| • | The PCM stores the conditions present when the DTC sets as Freeze Frame/Failure Records data. |
| • | A history DTC is stored. |
| • | The PCM commands the cooling fan to 100 percent. |
Conditions for Clearing the MIL/DTC
| • | The PCM turns OFF the MIL after the third consecutive trip the diagnostic has 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 Clear DTC Information function. |
Diagnostic Aids
| • | An inline connector could cause an intermittent DTC. Ensure to test for poor connections and pin retention at all inline connectors. Refer to system schematics for connectors and locations. |
| • | If the condition is not present, refer to Testing for Intermittent Conditions and Poor Connections . |
| • | Disconnect the harness connector of the cooling fan from the shroud. Inspect the exposed wires between the harness connector and the tubing. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
Step | Action | Values | 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 | |
Does the test lamp illuminate? | -- | Go to Step 3 | Go to Step 9 | |
3 | Test the cooling fan clutch control circuit of the cooling fan relay for a short to voltage or an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 4 |
4 | Test the cooling fan clutch control circuit of the cooling fan relay for a short to ground. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 5 |
5 |
Is the frequency less than the specified value? | OL | Go to Step 8 | Go to Step 6 |
6 | Command the Fan Control to 100 percent. Does the frequency fluctuate? | -- | Go to Step 7 | Go to Step 8 |
7 | Inspect for poor connections at the cooling fan relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 10 |
8 | Inspect for poor connections at the harness connector of the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 11 |
9 | Repair the ignition 1 voltage circuit of the cooling fan relay. Refer to Wiring Repairs . Did you complete the repair? | -- | Go to Step 12 | -- |
10 | Replace the cooling fan relay. Did you complete the replacement? | -- | Go to Step 12 | -- |
11 | Replace the PCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 12 | -- |
12 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
