Theory Of Operation

The Powertrain Control Module (PCM) sends a CAN bus message to the Totally Integrated Power Module (TIPM) requesting cooling fan operation. The TIPM grounds the coil for the requested Cooling Fan Relay through the radiator fan control circuit. The Cooling Fan Relay then provides battery voltage to the Cooling Fan Motor. Vehicles with diesel engines, certain export market vehicles and trailer tow packages are equipped with a pulse-width modulated (PWM) fan. The fan receives a duty cycle signal from the Totally Integrated Power Module (TIPM) on the Radiator Fan Speed Control circuit. Based on the requested fan speed from the PCM, the TIPM outputs a duty cycle signal on the Radiator Fan Speed Control circuit to the Radiator Cooling Fan. The Radiator Cooling Fan receives the duty cycle signal from the TIPM and controls the fan accordingly. The High or Low Speed Cooling Fan Relay is not used to control any components in a PWM system and have no external function. The TIPM connects to the Cooling Fan Relays through an internal connections and may set a DTC if the Cooling Fan Relays are removed or damaged.