Cooling Fan Functional Check

Electric Cooling Fan Diagnosis (Functional Test)

Refer to Engine Controls Schematics Coolant Fan Motor #1 and Coolant Fan Motor #2 for a wiring diagram Electrical Diagrams.

Circuit Description

The engine cooling fans receive power from two separate 30-amp maxifuses that are located in the underhood electrical center.

During low speed operation, the PCM supplies a ground path for the Cool Fan 1 relay through the control circuit for the low speed fans. This energizes the relay coil, closes the Fan 1 relay contacts, and supplies current to the engine cooling fan #1 motor. The ground path for engine cooling fan #1 motor is through the series/parallel cooling fan relay and the engine cooling fan #2 motor. The result is a series circuit with both fans running at low speed.

In order to command the high speed cooling fan operation, the PCM first supplies a ground path for the Cool Fan 1 relay through the low speed fans control circuit. After a 3-second delay, the PCM supplies a ground path for the Cool Fan 2 and the Cool Fan 3 relays through the high speed fans control circuit. During high speed operation, current is supplied to both engine cooling fan motors through their respective maxifuses. Each fan has its own ground path.

The PCM will command the low speed cooling fans operation during any of the following conditions:

VIN K

- When the A/C is requested and the ambient temperature is more than 50°C (122°F).
- When the engine coolant temperature exceeds 106°C (223°F).
- When the A/C refrigerant pressure is more than 190 psi (2 volts).
- When the ignition is off, and engine coolant temperature is more than 140°C (284°F).

VIN 1

- When the A/C is requested and the ambient temperature is more than 40°C (104°F).
- When the engine coolant temperature exceeds 100°C (212°F).
- When the A/C refrigerant pressure is more than 190 psi (2 volts).
- When the ignition is off, and the engine coolant temperature is more than 140°C (284°F).

The PCM will command the high speed cooling fans operation during any of the following conditions:

VIN K

- When the engine coolant temperature exceeds 110°C (230°F).
- When the A/C refrigerant pressure is more than 240 psi (2.5 volts).

VIN 1

- When the engine coolant temperature exceeds 108°C (226°F).
- When the A/C refrigerant pressure is more than 240 psi (2.5 volts).

Diagnostic Aids

Inspect for the following conditions:

- A poor connection at the PCM, the cooling fan relays, or the cooling fan motors. Inspect the harness connectors for the following conditions:

- Backed-out terminals
- Improper mating
- Broken locks
- Improperly-formed terminals
- Damaged terminals
- Poor terminal-to-wire connections
- A damaged harness-Inspect the wiring harness for damage.

Test Description

The numbers below refer to numbers on the diagnostic table.

2. The PCM will enable the engine cooling fans when certain Diagnostic Trouble Codes are set. Go to the applicable DTC Table first, before you proceed with this table.
3 Allow the engine coolant temperature to cool to less than 100°C (212°F) before proceeding with the diagnosis.

Electric Cooling Fan Functional Check