D Group 28 Design and Function 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 Intake Air Temperature and Humidity (IATH) Sensor is located in the air intake tube just downstream from the air filter canister.
Intake Manifold (Boost) Temperature Sensor 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 Intake Manifold (Boost) Temperature Sensor is located in the intake manifold. Intake Manifold Pressure Sensor The Intake Manifold Pressure Sensor contains a pressure sensitive diaphragm and an electrical amplifier. Mechanical pressure applied to the diaphragm causes the diaphragm to deflect and the amplifier to produce an electrical signal proportional to the deflection.
The Intake Manifold Pressure Sensor is located on the air inlet pipe before the intake manifold. 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. The Throttle Position Sensor is located above the accelerator pedal. 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.
Turbo Speed Sensor The Turbo Speed Sensor informs the EMS of the turbo shaft speed. The sensor does not read from the vanes, but reads from the shaft. The Engine Management System (EMS) Module uses this signal in conjunction with the VGT position sensor signal to control the speed of the turbocharger and therefore optimize the intake manifold pressure. The Turbo Speed Sensor is mounted in the center of the turbocharger. 6