Cooling Fan Run-on

The Powertrain Control Module (PCM) usually powers down 10 to 30 seconds after the ignition is turned OFF. Since the cooling fan is PCM controlled, the PCM may remain powered up for up to 7 minutes after the ignition is turned OFF to provide a ground in order to energize the cooling fan relay.

This is called a fan run-on and will occur if any of the following combinations of conditions exist when the ignition is turned OFF.
- Engine coolant temperature greater than 100°C (212°F) and intake air temperature greater than 80°C (176°F).
- Engine coolant temperature greater than 112°C (234°F) and intake air temperature greater than 70°C (158°F).
- Engine coolant temperature greater than 116°C (241°F).

The PCM and cooling fan will remain ON until these combinations of conditions no longer exist, up to a maximum of 7 minutes.

If the cooling fan is OFF when the PCM powers down, it will remain OFF regardless of any temperatures until the ignition is turned ON again.