Cooling Fan Control
The engine cooling fan system consists of one cooling fan and two relays with the L61 4 cylinder engine and two cooling fans and three relays with the L66 V6 engine. The relays are powered by the battery positive voltage circuit and controlled by a switched ground from the engine control module (ECM) or powertrain control module (PCM).
During operation, the ECM/PCM supplies the ground path for the cooling fan relays through the cooling fan relay control circuit. This energizes the cooling fan relay coil, closes the relay contacts, and supplies battery positive voltage from the cooling fan fuse through the cooling fan motor supply voltage circuit to the cooling fan. The cooling fan motor is grounded through its own ground circuit.
The ECM/PCM commands the fan on under the following conditions:
- Engine coolant temperature exceeds approximately 114°C (237°F) - L61/2.2L.
- Engine coolant temperature exceeds approximately 98°C (208°F) Low Fan Speed - L66/3.5L.
- Engine coolant temperature exceeds approximately 102°C (216°F) High Fan Speed - L66/3.5L.
- A/C refrigerant pressure exceeds 2,945 kPa (427 psi) - L61/2.2L.
- A/C refrigerant pressure exceeds 361 kPa (52 psi) Low Fan Speed - L66/3.5L.
- A/C refrigerant pressure exceeds 2100 kPa (300 psi) High Fan Speed - L66/3.5L.
- With the L66 V6 engine, when the engine coolant temperature exceeds 112°C (234°F) at key off, the fan high speed will run for up to 300 seconds. If within that time frame 102°C (216°F) is reached then fan speed will change from high to low speed. If within that time frame 99°C (210°F) is reached then fan speed will change from low to off.
The ECM/PCM commands the fan off under the following conditions:
- A/C is requested and engine speed exceeds 6,250 RPM - L61/2.2L.
- A/C is requested and engine speed exceeds 6,240 RPM - L66/3.5L.
- Engine coolant temperature exceeds approximately 99°C (210°F) turns the cooling fans from low to off - L66/3.5L