Purpose
The electric cooling fans are used to lower the temperature of the engine coolant flowing through the radiator. They are also used to cool the refrigerant (R134a) flowing through the A/C condenser.
Operation
The Powertrain Control Module (PCM) controls the operation of the cooling fans. This is accomplished by providing a ground path for the cooling fan relay coils. The relay contacts will close and complete the circuit between the fusible link at the battery junction block and the fan motors.
Power is supplied to the cooling fan motors through a fusible link and three 60 amp maxifuses. The 60 amp maxifuses are located in the underhood electrical center. The PCM Output Driver Module B output 1 is used to control Fan 1 operation. The PCM Output Driver Module B output 2 is used to control Fan 2 operation. The Driver Module outputs are monitored by the PCM. Before using the diagnostics found in this section be sure to perform the Diagnostic Circuit Check found in section 6A. If Diagnostic Trouble Codes P1651 or P1652 are present follow the appropriate diagnostic tables prior to performing diagnostics found in this section.
The PCM will complete the ground path for the Fan 1 relay under the following conditions:
| • | When engine temperature exceeds 100°C (212°F). |
| • | When A/C is requested (ambient temperature must be above 38 °C (100 °F). |
| • | When A/C refrigerant pressure is greater than 190 psi. |
| • | When the ignition is off and engine coolant temperature is greater than 106°C (222°F). |
Fan 2 is used for the increased demand on the cooling system due to A/C. The PCM will complete the ground path for the Fan 2 relay under the following conditions:
| • | When engine temperature exceeds 108°C (226°F). |
| • | When A/C refrigerant pressure is greater than 240 psi. |
When certain Diagnostic Trouble Codes (DTCs) are present, the PCM may command the cooling fans to run all the time. It is important to perform the Diagnostic Circuit check prior to diagnosing the engine cooling fans.
Diagnosis
The following Electric Cooling Fan Diagnostic Table will diagnose the PCM controlled cooling fans.
For specific system description, components and wiring, refer to Cooling Fans in Section 8A or the applicable Electric Cooling Fan diagnostic tables.
