Cooling Fan Description and Operation (LF1)
The engine cooling fan system is composed of one electric cooling fan, a series of 5 relays, the engine control module (ECM), and the associated wiring. The cooling fan assembly includes two separate resistors mounted in the cooling fan shroud. This combination of components enables the ECM to operate the cooling fan at 3 speeds using two fan control circuits.
Low Speed Operation
The ECM applies ground at the FAN 1 control circuit for the coil side of the cooling fan relay. The energized cooling fan relay completes a ground, through the switch side of the relay, for the coils of the cooling fan low speed relay and the cooling fan speed control relay. The speed control relay activates and supplies B+ to the coil side of the cooling fan high speed relay. The high speed relay remains inactive because the ECM is not commanding the FAN 2 control circuit ON. The energized low speed relay switch closes to supply B+ through the external low speed resistor, to the engine cooling fan motor. The result is cooling fan operation at a reduced speed.
Medium Speed Operation
The ECM applies ground at the FAN 2 control circuit for the coil side of the cooling fan high speed, and medium speed relays. The high speed relay remains inactive because the ECM is not commanding the FAN 1 control circuit ON. The average speed relay closes to supply B+ through the external average speed resistor, to the engine cooling fan motor. The result is cooling fan operation at a medium speed.
High Speed Operation
The ECM applies ground at the FAN 1 control circuit for the coil side of the cooling fan relay. The energized cooling fan relay completes a ground, through the switch side of the relay, for the coil of the cooling fan speed control relay. The energized speed control relay switch closes to supply B+ to the coil side of cooling fan high speed relay. Simultaneously, the ECM applies ground at the FAN 2 control circuit for the coil side of the cooling fan high speed relay. The energized high speed relay switch closes to supply B+ directly to the engine cooling fan motor, by-passing the external resistors. The result is cooling fan operation at full speed.
Cooling Fan Description and Operation
For cooling fan description and operation, refer to COOLING FAN DESCRIPTION AND OPERATION (LF1) or COOLING FAN DESCRIPTION AND OPERATION (LAU) .
Circuit/System Description
The engine cooling fan system is composed of one cooling fan, a series of 5 relays, the engine control module (ECM), and the associated wiring. The cooling fan assembly includes two individual resistors mounted to each side of the cooling fan shroud. This combination of components enables the ECM to operate the cooling fan at 3 speeds using two fan control circuits.
To operate the fan, the ECM activates the applicable relay by grounding the control circuit with a solid state device called a driver. The driver is equipped with a feedback circuit. The ECM can determine if the control circuit is open, shorted to ground, or shorted to a voltage by monitoring the feedback voltage.
Description and Operation
COOLING FAN DESCRIPTION AND OPERATION (LF1) or COOLING FAN DESCRIPTION AND OPERATION (LAU)
The engine control module (ECM) commands the cooling fan depending on cooling requirements. The ECM controls the cooling fan speed by commanding the cooling fan control module. The cooling fan control module supplies the power and ground circuits for the cooling fan. The ECM sends a pulse width modulated (PWM) signal to the cooling fan control module. The cooling fan control module interprets the signal and operates the cooling fan at the commanded speed.
COOLING FAN DESCRIPTION AND OPERATION (LF1) or COOLING FAN DESCRIPTION AND OPERATION (LAU)
The engine cooling fan system is composed of one cooling fan, a series of 5 relays, the engine control module (ECM), and the associated wiring. The cooling fan assembly includes two individual resistors mounted to each side of the cooling fan shroud. This combination of components enables the ECM to operate the cooling fan at 3 speeds using two fan control circuits.
To operate the fan, the ECM activates the applicable relay by grounding the control circuit with a solid state device called a driver. The driver is equipped with a feedback circuit. The ECM can determine if the control circuit is open, shorted to ground, or shorted to a voltage by monitoring the feedback voltage.
COOLING FAN DESCRIPTION AND OPERATION (LF1) or COOLING FAN DESCRIPTION AND OPERATION (LAU)
The engine control module (ECM) uses the engine coolant temperature sensor to monitor the engine for an over-temperature condition. This condition occurs when the coolant temperature is above a calibrated value. The ECM will alternately disable 2 groups of cylinders by turning OFF the fuel injectors. By switching between the 2 groups of cylinders, the ECM is able to reduce the temperature of the coolant.
- «COOLING FAN DESCRIPTION AND OPERATION (LF1)»(ref-652237-S24926922642014082300000) or «COOLING FAN DESCRIPTION AND OPERATION (LAU)»(ref-652237-S24580547552014082300000)
- «INSTRUMENT CLUSTER DESCRIPTION AND OPERATION»(ref-652250-S27488533322014082300000)
- «INDICATOR/WARNING MESSAGE DESCRIPTION AND OPERATION»(ref-652250-S37296746632014082300000)
The auxiliary coolant pump and cooling fan system provides a measure of prevention against fuel vaporization due to excessive engine temperatures. The engine control module (ECM) commands the auxiliary or after boil coolant pump ON when the engine coolant temperature exceeds a calibrated value after engine shut down. The ECM applies ground to the coil side of the auxiliary pump circuit board (PCB) relay. This energizes the coil and applies voltage directly to the pump motor through the switch side of the relay.
The indicator lamp for low coolant levels is located in and controlled by the instrument cluster (IPC). The level switch for coolant is located in the coolant's expansion tank. The switch remains open when surrounded by coolant. When the engine coolant level switch is closed for greater than 10 seconds, indicating low coolant, the IPC will turn ON the Low Coolant Indicator lamp. The lamp will also illuminate for approximately 3 seconds during the display test at the start of each ignition cycle.
COOLING SYSTEM DESCRIPTION AND OPERATION
The engine control module (ECM) commands the cooling fan ON depending on the engine cooling requirements. The ECM controls the cooling fan speed by commanding the cooling fan control module. The cooling fan control module supplies the power and ground circuits for the cooling fan. The ECM sends a pulse width modulated (PWM) signal voltage to the cooling fan control module. The cooling fan control module interprets the signal and operates the cooling fan at the commanded speed.
COOLING FAN DESCRIPTION AND OPERATION (LF1, LFW, LFX) or COOLING FAN DESCRIPTION AND OPERATION (LAU)
The engine cooling fan system is composed of one cooling fan, a series of 5 relays, the engine control module (ECM), and the associated wiring. The cooling fan assembly includes two resistors. This combination of components enables the ECM to operate the cooling fan at 3 speeds using two fan control circuits.
COOLING FAN DESCRIPTION AND OPERATION (LF1) or COOLING FAN DESCRIPTION AND OPERATION (LAU)
The engine control module (ECM) commands the cooling fan ON depending on the engine cooling requirements. The ECM controls the cooling fan speed by commanding the cooling fan control module. The cooling fan control module supplies the power and ground circuits for the cooling fan. The ECM sends a pulse width modulated (PWM) signal voltage to the cooling fan control module. The cooling fan control module interprets the signal and operates the cooling fan at the commanded speed.
COOLING FAN DESCRIPTION AND OPERATION (LF1, LFW, LFX) or COOLING FAN DESCRIPTION AND OPERATION (LAU)
The engine cooling fan system is composed of one cooling fan, a series of 5 relays, the engine control module (ECM), and the associated wiring. The cooling fan assembly includes two individual resistors mounted to each side of the cooling fan shroud. This combination of components enables the ECM to operate the cooling fan at 3 speeds using two fan control circuits.
COOLING FAN DESCRIPTION AND OPERATION (LF1) or COOLING FAN DESCRIPTION AND OPERATION (LAU)
The auxiliary coolant pump and cooling fan system provides a measure of prevention against fuel vaporization due to excessive engine temperatures. The engine control module (ECM) commands the auxiliary or after boil coolant pump ON when the engine coolant temperature exceeds a calibrated value after engine shut down. The ECM applies ground to the coil side of the auxiliary pump circuit board (PCB) relay. This energizes the coil and applies voltage directly to the pump motor through the switch side of the relay.
COOLING FAN DESCRIPTION AND OPERATION (LF1) or COOLING FAN DESCRIPTION AND OPERATION (LAU)
The auxiliary coolant pump and cooling fan system provides a measure of prevention against fuel vaporization due to excessive engine temperatures. The engine control module (ECM) commands the auxiliary or after boil coolant pump ON when the engine coolant temperature exceeds a calibrated value after engine shut down. The ECM applies ground to the coil side of the auxiliary pump circuit board (PCB) relay. This energizes the coil and applies voltage directly to the pump motor through the switch side of the relay.
COOLING SYSTEM DESCRIPTION AND OPERATION
The auxiliary coolant pump and cooling fan system provides a measure of prevention against fuel vaporization due to excessive engine temperatures. The engine control module (ECM) commands the auxiliary or after boil coolant pump ON when the engine coolant temperature exceeds a calibrated value after engine shut down. The ECM applies ground to the coil side of the auxiliary pump circuit board (PCB) relay. This energizes the coil and applies voltage directly to the pump motor through the switch side of the relay.
COOLING SYSTEM DESCRIPTION AND OPERATION
The optional coolant heater operates using 110 V AC external power and is designed to warm the coolant in the engine block area for improved starting in very cold weather. There is an internal thermal switch in the power cord that prevents system operation above -18 °C (0 °F). The coolant heater helps reduce fuel consumption when a cold engine is warming up. The unit is equipped with a detachable AC power cord. A weather shield on the cord is provided to protect the plug when not in use.