Electric Cooling Fans: Operation
Powertrain Control Module (PCM) activates cooling fans based on either air conditioning pressure, engine coolant temperature or transmission fluid temperature. Radiator cooling fan and transmission oil cooling fan operate on separate relays. Therefore, both fans will operate independently when one of three activation conditions are met. Cooling fans will not run during cranking until engine starts, regardless of coolant temperature, A/C pressure, and/or transmission fluid temperature.
Radiator cooling fan is a 2-speed electric motor. Low speed operation of radiator cooling fan is controlled by PCM through low speed radiator fan relay. Low speed radiator fan relay is located in power distribution center. See Fig 1 . If A/C clutch is not engaged, PCM actuates low speed relay when engine coolant temperature reaches about 210°F (99°C) and turns relay off when temperature drops to about 199°F (93°C). PCM will activate low speed radiator fan relay whenever A/C clutch is engaged according to A/C pressure and cut-out switches, regardless of engine coolant temperature and vehicle speed.
High speed radiator fan operation is controlled by PCM through high speed radiator fan relay. High speed radiator fan relay is located in power distribution center. See Fig 1 . PCM actuates high speed relay when engine coolant temperature reaches about 220°F (104°C) and turns relay off when temperature drops to about 210°F (99°C).
Transmission oil cooling fan is a single-speed electric motor. Operation of transmission oil cooling fan is controlled by PCM through transmission fan relay. Transmission fan relay is located in power distribution center. See Fig 1 . If radiator cooling fan is off, PCM actuates transmission fan relay when transmission fluid temperature reaches about 208°F (98°C) and turns relay off when temperature drops to about 200°F (93°C). If radiator cooling fan is on, PCM actuates transmission fan relay when transmission fluid temperature reaches about 192°F (89°C) and turns relay off when radiator cooling fan turns off. Radiator and transmission oil cooling fans will run if transmission's on-board diagnostic system records a malfunction that causes system to enter "Limp-in Mode".