Cooling Fan(s) Motor Control

The PCM 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 PCM is not grounding a fan control circuit, the cooling fan control module will detect a high voltage state (battery voltage). When the PCM 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 PCM to command four different fan speeds: Off, low, medium and high.

The PCM 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 99°C (210°F), on medium speed if the ECT is greater than 102°C (216°F) and on high speed if the ECT is greater than 105°C (221°F). The cooling fans will turn Off when the temperature drops below 95°C (203°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 PCM 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 PCM also runs the cooling fans based on A/C high side pressure. Refer to the HVAC for a cooling fan logic description on fan speed vs. A/C system pressure.