Circuit Description
Battery positive voltage is supplied to the cooling fan 1 relay from the COOL FAN #1 fuse. The powertrain control module (PCM) or engine control module (ECM) controls the cooling fan 1 relay by grounding the low speed cooling fan relay control circuit via an internal solid state device called a driver.
Battery positive voltage is supplied to the cooling fan 2 relay and the cooling fan 3 or S/P relay from the COOL FAN #2 fuse. The PCM/ECM controls the relays by grounding the high speed cooling fan relay control circuit.
When the PCM/ECM is commanding a relay ON, the voltage potential of the control circuit should be low, near 0 volts. When the PCM/ECM is commanding the control circuit to a relay, 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 PCM/ECM will monitor the control circuit for the following:
| • | A short to ground |
| • | A short to voltage |
| • | An open circuit |
| • | An open relay coil |
| • | An internally shorted or excessively low resistance relay coil |
When the PCM/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 1 Relay Control Circuit |
| • | DTC P0481 Cooling Fan 2 and 3 or S/P Relay Control Circuit |
| • | DTC P0691 Cooling Fan 1 Relay Control Circuit Low Voltage |
| • | DTC P0692 Cooling Fan 1 Relay Control Circuit High Voltage |
| • | DTC P0693 Cooling Fan 2 and 3 or S/P Relay Control Circuit Low Voltage |
| • | DTC P0694 Cooling Fan 2 and 3 or S/P Relay Control Circuit High Voltage |
Conditions for Running the DTC
| • | The ignition is ON. |
| • | 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
| • | The PCM/ECM detects an open, a short to ground, or a short to voltage on the cooling fan relay control circuit. |
| • | The above conditions are present for at least 30 seconds. |
Action Taken When the DTC Sets
| • | The PCM/ECM will illuminate the malfunction indicator lamp (MIL) during the second consecutive trip in which the diagnostic test has been run and failed. |
| • | The PCM/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 PCM/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. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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Listen for an audible click when the cooling fan 1 relay operates. Command both the ON and OFF states. Repeat the commands as necessary.
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Listen for an audible click when the cooling fan 2 and cooling fan 3 or S/P relays operate. Command both the ON and OFF states. Repeat the commands as necessary.
-
This step tests for voltage at the coil side of the cooling fan 1 relay. The COOL FAN #1 fuse supplies battery positive voltage to the coil side of the cooling fan 1 relay.
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 |
Does the cooling fan 1 relay turn ON and OFF with each command? | Go to Step 3 | Go to Step 4 | |
Do the cooling fan 2 and the cooling fan 3 or S/P relays turn ON and OFF with each command? | Go to Diagnostic Aids | Go to Step 6 | |
Does the test lamp illuminate? | Go to Step 5 | Go to Step 16 | |
5 |
Does the test lamp turn ON and OFF with each command? | Go to Step 12 | Go to Step 9 |
6 |
Does the test lamp illuminate? | Go to Step 7 | Go to Step 16 |
7 |
Does the test lamp turn ON and OFF with each command? | Go to Step 14 | Go to Step 8 |
8 |
Does the test lamp turn ON and OFF with each command? | Go to Step 13 | Go to Step 9 |
9 | Does the test lamp remain illuminated with each command? | Go to Step 11 | Go to Step 10 |
10 | Test the control circuit of the appropriate relay for a short to voltage or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 21 | Go to Step 15 |
11 | Test the control circuit of the appropriate relay for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 21 | Go to Step 15 |
12 | Inspect for poor connections at the cooling fan 1 relay. 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 21 | Go to Step 17 |
13 | Inspect for poor connections at the cooling fan 2 relay. 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 21 | Go to Step 18 |
14 | Inspect for poor connections at the cooling fan 3 or S/P relay. 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 21 | Go to Step 19 |
15 | Inspect for poor connections at the harness connector of the powertrain control module (PCM)/engine control module (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 21 | Go to Step 20 |
16 | Repair the battery positive voltage circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 21 | -- |
17 | Replace the cooling fan 1 relay. Did you complete the replacement? | Go to Step 21 | -- |
18 | Replace the cooling fan 2 relay. Did you complete the replacement? | Go to Step 21 | -- |
19 | Replace the cooling fan 3 or S/P relay. Did you complete the replacement? | Go to Step 21 | -- |
20 | Replace the PCM/ECM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | Go to Step 21 | -- |
21 |
Does the DTC reset? | Go to Step 2 | System OK |
