FILTER OUTLET THERMOCOUPLE (A4) INTAKE MANIFOLD (BOOST) TEMPERATURE SENSOR This thermocouple is used to measure exhaust gas temperature at the outlet face of the DPF filter. The DPF ECU monitors this temperature and uses it for system fault detection. The Intake Manifold (Boost) Temperature Sensor is a thermistor whose resistance varies inversely to temperature. The sensor has a negative temperature coefficient, which means the sensor resistance will decrease as the inlet air temperature increases. The filter outlet thermocouple is located on the side of the DPF and is positioned after the DPF filter. The Intake Manifold (Boost) Temperature Sensor is located in the intake manifold.
FLAME THERMOCOUPLE (A2) This thermocouple is used to measure exhaust gas temperature within the flame region of the DPF during regeneration. The DPF ECU monitors this temperature to detect the existence of the flame. Fault codes may result if the system is unable to light the flame or if there are multiple flame losses. MASTER AIR VALVE The master air valve is located inside of the atomization module and is controlled by the DPF ECU. The valve opens when the engine starts and closes when the engine shuts-down. The compressed air supplied through this valve and is used to keep the non-catalyzed DPF fuel nozzle clean during normal operation.
The master air valve is also used to assist with fuel atomization during regeneration. The flame thermocouple is located on the bottom of the DPF. FUEL PRESSURE SENSOR The fuel pressure sensor contains a diaphragm that senses fuel pressure. A pressure change causes the diaphragm to flex, inducing a stress or strain in the diaphragm. The resistor values in the sensor change in proportion to the stress applied to the diaphragm and produces an electrical output. SERIAL COMMUNICATION PORT The serial communication port is a six or nine pin connector used to access the system diagnostics and reprogramming functions.
This connector conforms to the SAE standards and is located under the dashboard to the left of the steering column. The Fuel Pressure Sensor is located on top of the fuel filter housing. THROTTLE POSITION (TP) SENSOR The Throttle Position Sensor is a potentiometer that is mechanically linked to the accelerator pedal. A potentiometer is a variable resistor whose resistance will change as the pedal is pressed. As the resistance changes, the signal voltage of the sensor changes indicating the accelerator pedal position. INTAKE AIR TEMPERATURE AND HUMIDITY (IATH) SENSOR The Intake Air Temperature and Humidity (IATH) Sensor contains a thermistor and a capacitive sensor.
The resistance of the thermistor varies inversely to temperature. The output of the capacitive sensor increases as the humidity of the surrounding air increases. By monitoring the signals from both portions of the sensor, the Engine Management System (EMS) Module calculates the temperature and humidity of the air passing through the air filter housing. The Throttle Position Sensor replaces the mechanical linkage for fuel control. The sensor is located under the accelerator pedal. The “drive by wire” pedal is designed to provide a system that “feels” similar to the standard type of accelerator pedal and mechanical linkage.
The sensor is designed to improve the driver's control by reducing sensitivity to chassis motion. This sensor provides the driver's fuel request input to the VECU. The Intake Air Temperature and Humidity (IATH) Sensor is located in the air intake tube just downstream from the air filter canister. Page 10 DESCRIPTION AND OPERATION