| Table 1: | Cooling Fan 1 Relay |
| Table 2: | Cooling Fan 2 Relay |
Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
Circuit/System Description
The powertrain control module (PCM) controls cooling fan operation in either high speed or low speed mode, depending on cooling requirements. To activate the fan, the PCM applies ground to the coil side of the applicable fan relay. This energizes the coil and pulls the switch side of the relay closed.
In low speed operation, the PCM applies ground to the coil side of the low speed fan 1 relay. This energizes the coil and applies voltage directly to the cooling fan through the switch side of the fan 1 relay. The cooling fan is connected in series to the fan resistor through the de-energized fan 2 relay. The series circuit operates the fan at low speed.
In high speed operation, the PCM applies a ground to the coil side of the low speed fan relay and the high speed fan 2 relay. When energized, the fan 2 relay a provides a direct path to ground for the cooling fan through the switch side of the relay. Simultaneously, the fan 1 relay continues to provide ignition voltage to cooling fan which enables the fan to operate at high speed.
Diagnostic Aids
| • | The fan relay electrical contacts may be pitted or sticking. Replace the relay, if tapping gently on the relay, or wiggling the relay causes a change in the relays operation. |
| • | The performance of the cooling relay may be affected by temperature. Check the relay after sitting outside overnight and after running the engine 30 minutes. |
Use the following relay cavity table in order to locate the correct cavities to probe during diagnosis. The table layout corresponds to the cavity layout of the relay block.
Terminal Identification | ||
|---|---|---|
Relay Controlled Output | Relay Switch B+ | Relay Coil Control |
Relay Coil Ignition | ||
Front of Vehicle | ||
Terminal Identification | ||
|---|---|---|
Relay Controlled Input | Ground | Relay Coil Control |
Relay Controlled Output | ||
Relay Coil Ignition | ||
Front of Vehicle | ||
Reference Information
Schematic Reference
Connector End View Reference
Cooling System Connector End Views
Electrical Information Reference
DTC Type Reference
Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Circuit/System Verification
- Verify the HVAC system operates correctly.
- Ignition ON, observe that the fan is not activated.
| ⇒ | If an HVAC system condition is found, repair the HVAC condition first. Refer to Diagnostic Starting Point - Heating, Ventilation and Air Conditioning. |
Circuit/System Testing
- Ignition OFF, disconnect each cooling fan relay one at a time.
- Ignition ON, observe that the cooling fans are not activated.
- If all circuits test normal, test or replace the cooling fan relay.
Important: The following tests must be performed on each cooling fan relay.
| ⇒ | If the fan is activated, test for a short to voltage in the relay controlled output circuit. |
| ⇒ | If the fan is not activated, test for a short to ground in the relay coil control circuits. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
