Circuit Description
Battery positive voltage is supplied to the coolfan 1 relay from the coolfan 1 fuse. The powertrain control module (PCM) controls the coolfan 1 relay by grounding the low speed coolfan relay control circuit 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 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 |
| • | An open relay coil |
| • | An internally shorted or excessively low resistance relay coil. |
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 voltage is between 6 and 18 volts. |
| • | The engine speed is more than 400 RPM. |
Conditions for Setting the DTC
| • | An improper voltage level has been detected on the low speed coolfan relay control circuit. |
| • | The above conditions are 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 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
Check for the following conditions:
| • | A faulty connection at the PCM, inspect the harness connectors for the following conditions. |
| - | Backed out terminals |
| - | Improper mating |
| - | Broken locks |
| - | Improperly formed or damaged terminals |
| - | Faulty terminal to wire connections |
| • | Inspect the wiring harness for damage. |
| • | If the harness appears to be OK, disconnect the PCM, turn the ignition ON and observe a digital multimeter (DMM) connected between the low speed coolfan relay control circuit of the coolfan 1 relay and ground at the PCM harness connector. While moving connectors and the wiring harness related to the coolfan 1 relay, a change in voltage will indicate the location of the fault. |
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 numbers below refer to the step numbers on the diagnostic table.
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Listen for an audible click when the coolfan 1 relay operates. 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 coolfan 1 relay. The coolfan 1 fuse supplies battery positive voltage to the coil side of the coolfan 1 relay.
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Verifies that the PCM is providing ground to the coolfan 1 relay.
-
Tests if ground is constantly being applied to the coolfan 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 Engine Cooling Diagnostic System Check? | Go to Step 2 | |
Does the coolfan 1 relay 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 10 | |
Does the test lamp turn ON and OFF with each command? | Go to Step 8 | Go to Step 5 | |
Does the test lamp remain illuminated with each command? | Go to Step 7 | Go to Step 6 | |
6 | Test the control circuit of the coolfan 1 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 14 | Go to Step 9 |
7 | Test the control circuit of the coolfan 1 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 14 | Go to Step 9 |
8 | Inspect for poor connections at the coolfan 1 relay. Refer to the following procedures in Wiring Systems. Did you find and correct the condition? | Go to Step 14 | Go to Step 12 |
9 | Inspect for poor connections at the harness connector of the PCM. Refer to the following procedures in Wiring Systems. Did you find and correct the condition? | Go to Step 14 | Go to Step 13 |
10 | Test the battery positive voltage circuit for an open or a short to ground. Refer to the following procedures in Wiring Systems: Did you find and correct the condition? | Go to Step 14 | Go to Step 11 |
11 | Repair the coolfan motor supply voltage circuit for a short to ground. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 14 | -- |
12 | Replace the coolfan 1 relay. Did you complete the replacement? | Go to Step 14 | -- |
13 |
Important: Perform the set up procedure for the PCM. Replace the PCM. Refer to Powertrain Control Module Replacement in Engine Controls. Did you complete the replacement? | Go to Step 14 | -- |
14 |
Does the DTC reset? | Go to Step 2 | System OK |
