Circuit/System Description
The radiator coolant temperature (RCT) sensor is a variable resistor that measures the temperature of the radiator coolant. The ECM supplies 5 V to the RCT sensor signal circuit and supplies a ground for the low reference circuit.
The radiator coolant temperature (RCT) sensor is a variable resistor that measures the temperature of the radiator coolant. The ECM supplies 5 V to the RCT sensor signal circuit and supplies a ground for the low reference circuit.
The following table illustrates the difference between temperature, resistance, and voltage
| RCT | RCT Resistance | RCT Signal Voltage |
|---|---|---|
| Cold | High | High |
| Warm | Low | Low |
The electro-viscous (EV) cooling fan clutch system enables the engine control module (ECM) to change the speed of the pulley driven cooling fan in relation to the engine speed. Ignition voltage is supplied directly to the fan clutch solenoid valve. The ECM uses two output drivers and a parallel circuit to directly control the EV fan clutch solenoid valve. The ECM controls the solenoid valve by pulse width modulating (PWM) the parallel control circuits to ground, with a solid state device called a driver. The ECM changes the cooling fan speed by increasing or decreasing the solenoid valve ON time, known as duty cycle.
The electro-viscous (EV) cooling fan clutch system enables the engine control module (ECM) to change the speed of the pulley driven cooling fan in relation to the engine speed. Ignition voltage is supplied directly to the fan clutch solenoid valve. The ECM uses two output drivers and a parallel circuit to directly control the EV fan clutch solenoid valve. The ECM controls the solenoid valve by pulse width modulating (PWM) the parallel control circuits to ground, with a solid state device called a driver. The ECM changes the cooling fan speed by increasing or decreasing the solenoid valve ON time, known as duty cycle.
The electro-viscous (EV) cooling fan clutch system enables the engine control module (ECM) to change the speed of the pulley driven cooling fan in relation to the engine speed. Ignition voltage is supplied directly to the fan clutch solenoid valve. The ECM uses two output drivers and a parallel circuit to directly control the EV fan clutch solenoid valve. The ECM controls the solenoid valve by pulse width modulating (PWM) the parallel control circuits to ground, with a solid state device called a driver. The ECM changes the cooling fan speed by increasing or decreasing the solenoid valve ON time, known as duty cycle.
The engine control module (ECM) uses the cooling fan speed signal in order to determine the actual fan speed in relation to the desired fan speed, and to reduce the cooling fan noise while maintaining powertrain cooling requirements. The ECM supplies a 5-volt reference and low reference circuit to the fan speed sensor in the cooling fan clutch. The speed sensor returns a signal pulse through the signal circuit in response to the reluctor track, which is also integral to the cooling fan clutch assembly.
The engine control module (ECM) uses the engine coolant temperature (ECT) sensor to monitor the engine for an over-termperature condition. This condition occurs when the coolant temperature is above a calibrated value for a calibrated length of time. The ECM will disable half of the cylinders by turning OFF the fuel injectors. By disabling half of the cylinders, the ECM is able to reduce the temperature of the coolant.
The engine control module (ECM) monitors temperature difference between the engine coolant temperature (ECT) sensor and the radiator coolant temperature (RCT) sensor during a cold start-up. The purpose of this diagnostic is to analyze the engine coolant thermostat for being stuck open.
The low engine coolant level indicator lamp is located in, and controlled by the instrument panel cluster (IPC). The engine coolant level switch is located in the engine coolant surge tank. The switch remains closed when surrounded by coolant. When the engine coolant level switch is open 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.
The optional coolant heater is a 1,000 watt heating element that mounts in the engine block in place of an existing anti-freeze plug. The coolant heater operates using an external 110 volt AC power source and is designed to warm the coolant in the engine block, for improved starting in very cold weather. The coolant heater also helps reduce fuel consumption when a cold engine is warming up. The detachable AC power cord allows the coolant heater to operate at all temperatures whenever it is connected to an AC power source. The power cord is also equipped with a weather shield to protect the plug when not in use.
The optional coolant heater is a heating element that mounts in the engine block in place of an existing anti-freeze plug. The coolant heater operates using an external 110 volt AC power source and is designed to warm the coolant in the engine block for improved starting in very cold weather. The coolant heater also helps reduce fuel consumption when a cold engine is warming up. The detachable AC power cord contains an internal thermal switch that opens, to prevent operation when the ambient temperature is warmer than -10°C (14°F), and closes at -18°C (0°F) to allow operation. The power cord is also equipped with a weather shield to protect the plug when not in use.