Circuit Description
Ignition 1 Voltage is supplied to the coil of the engine cooling fan relay 1 and engine cooling fan relay 2. The switch side of the engine cooling fan relay 2 is in the ground path for the fan motor high speed. The powertrain control module (PCM) controls the high speed relay by grounding the 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 commands a component ON, the voltage potential of the control circuit should be low, near 0 volts. When the PCM commands 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 fault line status changes causing this type B DTC to set. The relay controls the high current flow to the cooling fans. This allows the PCM driver to only have to control the relatively low current used by the relay.
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 voltage is between 10 and 18 volts. |
| • | The engine speed is more than 400 RPM. |
Conditions for Setting the DTC
| • | The PCM detects that the commanded state of the driver and the actual state of the control circuit do not match. |
| • | The above conditions are present for at least 5 seconds. |
Action Taken When the DTC Sets
| • | The PCM illuminates the malfunction indicator lamp (MIL) during the second consecutive ignition cycle that the diagnostic test runs and fails. |
| • | The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the PCM stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the PCM records the operating conditions at the time of the failure. The PCM writes the operating conditions to the Freeze Frame and updates the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The PCM turns OFF the MIL after the third consecutive ignition cycle in which the diagnostic runs and does not fail. |
| • | A History DTC clears after 40 consecutive warm-up cycles have occurred without a malfunction. |
| • | The Last Test Failed (current DTC) clears when the diagnostic runs and passes. |
| • | 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 engine cooling fan relay 2 control circuit and ground at the PCM harness connector. While moving connectors and the wiring harness related to the engine cooling fan 2 relay, a change in voltage will indicate the location of the fault. |
Using the Freeze Frame/Failure Records data may aid in locating an intermittent condition. If you cannot duplicate the DTC, the information included in the Freeze Frame/Failure Records data can aid in determining the distance travelled since the DTC reported a pass and/or fail. Operate the vehicle within the same freeze frame conditions (RPM, load, vehicle speed, temperature, etc.) that you observed. This will isolate when the DTC failed.
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 engine cooling fan relay 2 operates. Command both the ON and OFF states. Repeat the commands as necessary.
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This check can detect a partially shorted coil which would cause excessive current flow. Leaving the circuit energized for 2 minutes allows the coil to warm up. When warm, the coil may open (Amps drop to 0), or short (goes above 0.75 Amps).
-
If you do not find any trouble in the control circuit or the connection at the PCM, the PCM may be faulty.
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 engine cooling fan relay 2 turn ON and OFF with each command? | Go to Step 3 | Go to Step 5 | |
Does the current draw measure between 0 and 0.75A? | Go to Diagnostic Aids | Go to Step 4 | |
4 |
Did you find and correct the condition? | Go to Step 12 | Go to Step 8 |
5 |
Does the test lamp turn ON and OFF with each command? | Go to Step 8 | Go to Step 6 |
6 | Test the engine cooling fan relay 2 supply voltage circuit for 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 7 |
7 | Test the engine cooling fan relay 2 control circuit for 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 |
8 | Inspect for a poor connection at the harness connector of the 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 12 | Go to Step 10 |
9 | Inspect for poor connections at the harness connector of the PCM. 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 12 | Go to Step 11 |
10 | Replace the fan 2 relay. Refer to Cooling Fan Relay Replacement . Did you complete the replacement? | Go to Step 12 | -- |
|
Important: The replacement PCM must be programmed. 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 |
