Scheme 589
For a complete wiring diagram, refer to appropriate SYSTEM WIRING DIAGRAMS article .
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. 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 connection and may set a DTC if the Cooling Fan Relays are removed or damaged.
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. 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 connection and may set a DTC if the Cooling Fan Relays are removed or damaged.
The vehicle speed sensor rationality is a continuous test that monitors the vehicle speed sensor for lack of activity. The rationality will not run if a limp-in exists for MAP, Throttle Position, and Engine Coolant Temperature. If vehicle speed sensor is below a minimum threshold for a period of time after the vehicle is operated at a sufficient load, a failure will be indicated.
The vehicle speed sensor rationality is a continuous test that monitors the vehicle speed sensor for lack of activity. The rationality will not run if a limp-in exists for MAP, Throttle Position, and Engine Coolant Temperature. If vehicle speed sensor is below a minimum threshold for a period of time after the vehicle is operated at a sufficient load, a failure will be indicated.
The objective of the Idle Speed Rationality monitor is to evaluate the ability of the idle speed control system to achieve and maintain a steady idle, by monitoring engine RPM during idle. If engine RPM is not within a calibrated deadband of target idle speed, a timer is started. If the timer reaches a maximum threshold without any sign of the RPM trending towards control, a fault is generated.
The objective of the Idle Speed Rationality monitor is to evaluate the ability of the idle speed control system to achieve and maintain a steady idle, by monitoring engine RPM during idle. If engine RPM is not within a calibrated deadband of target idle speed, a timer is started. If the timer reaches a maximum threshold without any sign of the RPM trending towards control, a fault is generated.
Spark adjustment during a cold start is intended to provide quick response to idle speed variations. The spark adjust diagnostics monitors spark advance on a cold start over a period of time, then compares the average spark advance to a threshold.
The objective of the Dynamic Crankshaft Fuel Control (DCFC) is to reduce the fuel as much as possible during a cold start. The DCFC begins subtracting fuel from a high limit upon a cold start and keeps removing fuel in an attempt to get to a calibrated lean limit. DCFC stops removing fuel when rough idle is detected or the lean limit is reached.
The A/C pressure transducer monitors the pressures in the high side of the A/C refrigerant system through its connection to a fitting on the A/C discharge line and its internal resistance changes in response to the pressures it monitors. The Totally Integrated Power Module (TIPM) provides a five Volt reference signal and a sensor ground to the A/C pressure transducer, then monitors the output voltage of the transducer on a sensor return circuit to determine refrigerant pressure the TIPM busses the reads to PCM. The PCM is programmed to respond to this and other sensor inputs by controlling the operation of the A/C clutch and the radiator cooling fan to help optimize A/C system performance and to protect the A/C system components from damage. The PCM will request disengagement of the A/C clutch when high side pressure rises above 3219 kPa (476 psi) and re-engage the clutch when high side pressure drops below 2937 kPa (426 psi). The PCM will also disengage the A/C clutch if the high side pressure drops below 110 kPa (16 psi) and will re-engage the clutch when the high side pressure rises above 220 kPa (32 psi). When the refrigerant pressure rises above 1655 kPa (240 psi), the PCM will actuate the cooling fan.
The A/C pressure transducer monitors the pressures in the high side of the A/C refrigerant system through its connection to a fitting on the A/C discharge line and its internal resistance changes in response to the pressures it monitors. The Totally Integrated Power Module (TIPM) provides a five Volt reference signal and a sensor ground to the A/C pressure transducer, then monitors the output voltage of the transducer on a sensor return circuit to determine refrigerant pressure the TIPM busses the reads to PCM. The PCM is programmed to respond to this and other sensor inputs by controlling the operation of the A/C clutch and the radiator cooling fan to help optimize A/C system performance and to protect the A/C system components from damage. The PCM will request disengagement of the A/C clutch when high side pressure rises above 3219 kPa (476 psi) and re-engage the clutch when high side pressure drops below 2937 kPa (426 psi). The PCM will also disengage the A/C clutch if the high side pressure drops below 110 kPa (16 psi) and will re-engage the clutch when the high side pressure rises above 220 kPa (32 psi). When the refrigerant pressure rises above 1655 kPa (240 psi), the PCM will actuate the cooling fan.
The Electronic Throttle Control (ETC) motor is controlled by the Powertrain Control Module (PCM). The DC motor located in the throttle body drives the throttle blade. In order to decrease idle speed, along with spark and fuel delivery changes the PCM commands the throttle closed reducing air flow into the engine and the idle speed decreases. In order to increase idle speed, the PCM commands the throttle plate open allowing more air to pass the throttle plate.
The Electronic Throttle Control (ETC) motor is controlled by the Powertrain Control Module (PCM). The DC motor located in the throttle body drives the throttle blade. In order to decrease idle speed, along with spark and fuel delivery changes the PCM commands the throttle closed reducing air flow into the engine and the idle speed decreases. In order to increase idle speed, the PCM commands the throttle plate open allowing more air to pass the throttle plate.
The Electronic Throttle Control (ETC) motor is controlled by the Powertrain Control Module (PCM). The DC motor located in the throttle body drives the throttle blade. In order to decrease idle speed, along with spark and fuel delivery changes the PCM commands the throttle closed reducing air flow into the engine and the idle speed decreases. In order to increase idle speed, the PCM commands the throttle plate open allowing more air to pass the throttle plate.
The Electronic Throttle Control (ETC) motor is controlled by the Powertrain Control Module (PCM). The DC motor located in the throttle body drives the throttle blade. In order to decrease idle speed, along with spark and fuel delivery changes the PCM commands the throttle closed reducing air flow into the engine and the idle speed decreases. In order to increase idle speed, the PCM commands the throttle plate open allowing more air to pass the throttle plate.
The Electronic Throttle Control (ETC) motor is controlled by the Powertrain Control Module (PCM). The DC motor located in the throttle body drives the throttle blade. In order to decrease idle speed, along with spark and fuel delivery changes the PCM commands the throttle closed reducing air flow into the engine and the idle speed decreases. In order to increase idle speed, the PCM commands the throttle plate open allowing more air to pass the throttle plate.
The Electronic Throttle Control (ETC) motor is controlled by the Powertrain Control Module (PCM). The DC motor located in the throttle body drives the throttle blade. In order to decrease idle speed, along with spark and fuel delivery changes the PCM commands the throttle closed reducing air flow into the engine and the idle speed decreases. In order to increase idle speed, the PCM commands the throttle plate open allowing more air to pass the throttle plate.
The Electronic Throttle Control (ETC) motor is controlled by the Powertrain Control Module (PCM). The DC motor located in the throttle body drives the throttle blade. In order to decrease idle speed, along with spark and fuel delivery changes the PCM commands the throttle closed reducing air flow into the engine and the idle speed decreases. In order to increase idle speed, the PCM commands the throttle plate open allowing more air to pass the throttle plate.
The primary 5-Volt Supply circuit supplies the Crankshaft Position Sensor (CKP), Oil Pressure Sensor (OPS), Throttle Body Assembly, A/C Pressure Transducer, and Accelerator Pedal Position (APP) Sensor 1. For self protection, if the 5-Volt Supply circuit is shorted to ground or if one of the sensors is internally shorted, the Powertrain Control Module (PCM) will turn off the 5-Volt Supply circuit until the next ignition cycle.
The primary 5-Volt Supply circuit supplies the Crankshaft Position Sensor (CKP), Oil Pressure Sensor (OPS), Throttle Body Assembly, and Accelerator Pedal Position (APP) Sensor 1. For self protection, if the 5-Volt Supply circuit is shorted to ground or if one of the sensors is internally shorted, the Powertrain Control Module (PCM) will turn off the 5-Volt Supply circuit until the next ignition cycle.