The electric cooling fan(s) are used to cool engine coolant
flowing through the radiator. They are also used to cool the refrigerant (R134a)
flowing through the A/C condenser.
The electric cooling fans are controlled by the PCM. The PCM controls
the ground path for the three cooling fan relays. The relays are used to control
the high current flow to power the cooling fan motors. Both fans operate together.
When minimum cooling is required, the PCM energizes the low speed cooling
fan relay #1, and both fans operate at low speed since the fans are connected
in series through the series/parallel cooling fan relay #2. When maximum
cooling is required, the PCM energizes all three cooling fan relays. The
left hand coolant fan is still powered through the low speed cooling fan
relay #1, but is now grounded through the series/parallel cooling fan relay
#2 and operates at high speed. The right hand coolant fan is powered directly
through the high speed cooling fan relay #3 and also operates at high speed.
PCM will command fan operation when:
Low Speed Fan Operation
| • | Engine coolant temperature exceeds approximately 106°C (229°F). |
| • | Transmission fluid temperature exceeds 150°C (302°F). |
| • | A/C operation is requested. |
| • | After the vehicle is shut OFF if the coolant temperature at key-off
is more than 151°C (304°F) and system voltage was more than 12 volts.
The fans will stay ON for approximately 3 minutes. |
The fans will switch from low to OFF when the coolant drops below 102°C
(216°F).
High Speed Fan Operation
| • | Engine coolant temperature reaches 112°C (234°F). |
| • | Transmission temperature is more than 151°C (304°F). |
The fans will switch from high to low (except DTCs set) when the coolant
drops below 106°C (229°F).
