L300 V6-3.0L VIN R (2001)
Coolant Temperature Sensor/Switch (For Computer): Description and Operation
Cooling Fan(s) Motor Control
The ECM controls both cooling fan motors at all times by independently grounding two logic circuits (fan control 1 and fan control 2) to the cooling fan
control module. When the ECM is not grounding a fan control circuit, the cooling fan control module will detect a high voltage state (battery voltage).
When the ECM is grounding a fan control circuit, the cooling fan control module will detect a low voltage state (ground). The combination of these
high/low voltage states at the cooling fan control module allows the ECM to command four different fan speeds: Off, low, medium and high.
The ECM may ground fan control 1 and/or fan control 2 based on the reading from the ECT sensor. Under normal operating conditions, both cooling
fans operate on low speed whenever the ECT is greater than 96°C (204°F), on medium speed if the ECT is greater than 99°C (210°F) and on high speed
if the ECT is greater than 102°C (216°F). The cooling fans will turn Off when the temperature drops below 92°C (198°F). If the engine is turned Off
and the ECT is above 105°C (221°F), the cooling fans will run on low speed for 7 minutes regardless of how fast the ECT cools down. If the engine is
turned Off and the ECT is above 110°C (230°F), the cooling fans will run on low speed for 8.5 minutes regardless of how fast the ECT cools down. If a
low/high ECT sensor circuit fault (DTC P0117 or P0118) is set, the ECM will command the cooling fan control module to run the fans on high speed to
protect the engine and transaxle until the condition is corrected. The ECM also runs the cooling fans based on A/C high side pressure. Refer to HVAC
for a cooling fan logic description on fan speed vs. A/C system pressure.
