Circuit Description
Battery positive voltage is supplied to the control side of the cooling fan s/p relay and the control side of the cooling fan 2 relay through the cool fan 1 fuse. Battery positive voltage is supplied to the load side of the cooling fan 2 relay through the cool fan 2 fuse. The powertrain control module (PCM) controls the relays by grounding the cooling fan 2 relay control circuit via 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 which is monitored by the PCM. When the PCM is commanding a component on, the voltage potential of the control circuit should be low (near 0 volts). When the PCM is commanding the control circuit to a component off, 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 will monitor the control circuit for the following:
| • | A short to ground |
| • | A short to voltage |
| • | An open circuit |
When the PCM detects any of the above conditions, the DTC will set and the affected driver will be disabled.
Conditions for Running the DTC
| • | The ignition is ON. |
| • | The system voltage is between 9 and 18 volts. |
Conditions for Setting the DTC
| • | An improper voltage level has been detected on the high speed cooling fan relay control circuit. |
| • | The above conditions are present for at least 30 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 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 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/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 number(s) below refer to the step number(s) on the diagnostic table.
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Listen for an audible click when the cooling fan s/p and the cooling fan 2 relays operate. Command both the ON and OFF states. Repeat the commands as necessary.
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Tests for voltage at the coil side of the cooling fan 2 relay. The cool fan 2 fuse supplies power to the coil side of the cooling fan 2 relay.
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Verifies that the PCM is providing ground to the cooling fan 2 relay.
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Tests if ground is constantly being applied to the cooling fan 2 relay.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Engine Cooling Schematics | |||
1 | Did you perform the Engine Cooling Diagnostic System Check? | Go to Step 2 | |
|
Important: The cooling fan 1 and 2 relays and fuses are improperly identified in the underhood fuse block. Refer to Electrical Center Identification Views in Wiring Systems for proper identification.
Does the cooling fan s/p and the cooling fan 2 relays turn ON and OFF with each command? | Go to Diagnostic Aids | Go to Step 3 | |
Does the test lamp illuminate? | Go to Step 4 | Go to Step 8 | |
Does the test lamp turn ON and OFF with each command? | Go to Step 9 | Go to Step 5 | |
Does the test lamp remain illuminated with each command? | Go to Step 7 | Go to Step 6 | |
6 | Test the high speed cooling fan relay control circuit of the cooling fan s/p relay and the cooling fan 2 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 12 | Go to Step 9 |
7 | Test the high speed cooling fan relay control circuit of the cooling fan s/p relay and the cooling fan 2 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 12 | Go to Step 9 |
8 | Test the battery positive voltage circuit of the cooling fan s/p relay and the cooling fan 2 relay for an open or a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 12 | Go to Step 10 |
9 | Inspect for poor connections at the harness connector of the PCM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 12 | Go to Step 11 |
10 | Repair the cooling fan motor supply voltage circuit for a short to ground. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 12 | -- |
11 |
Important: Perform the programming procedure for the PCM. Replace the PCM. Refer to Powertrain Control Module Replacement in Engine Controls. Did you complete the replacement? | Go to Step 12 | -- |
12 |
Does the DTC reset? | Go to Step 2 | System OK |
