ELECTRONIC CONTROL SYSTEM MAF / IAT RIGHT BANK INJECTORS X1 X1 LEFT BANK INJECTORS X2 X2 IAT X3 X3 X1-7 IAT X1 IDM X1-6 GRD X1-8 ECT X2 X2-1 EOT X3 X4 ECT X2-14 MAT IAH RELAY EGR DRIVE MODULE ECM VOLTAGE R R 1 2 EOT SENSOR R 2 ECM MICRO- PROCESSOR MAT GLOW PLUG RELAY BCS R 1 REFERENCE VOLTAGE IPR EGR VALVE Temperature Sensor Operation • There are four, two-wire temper- ature sensors on the VT 275 engine. Each sensor contains a resistor whose value varies depend- ing on temperature. The ECM supplies a separate reference voltage to each temperature sensor. Then, the sensor conditions its voltage to produce the sensor signal. signal voltage is high.
When the temperature is high, the resistance is low and the signal voltage is low. Manifold Air Temperature (MAT) Sensor The MAT sensor is mounted towards the front of the left bank leg of the intake manifold. The MAT sensor measures the temperature of the air in the intake manifold. The ECM uses this information in calculations that control the EGR valve operation. Engine Coolant Temperature (ECT) Sensor The ECT sensor is mounted in the front cover. The body of the sensor is exposed to coolant as it returns from the cylinder heads.
The ECT signal is input into the optional engine warning protection system, coolant compensation, glow plug operation and the instrument cluster temperature gauge. Sensor Circuit A temperature variable resistor is a thermistor. Each thermistor is connected to a current-limiting resistor of fixed value within the ECM. The thermistor and the resistor make a series circuit with a reference voltage applied at one end and a ground at the other. The voltage in the circuit between the two resistors changes as the thermistor's resistance changes.
When the temperature is low, the sensor's resistance is high and the Intake Air Temperature (IAT) Sensor The IAT sensor is contained within the Mass Air Flow (MAF) sensor housing. The MAF sensor is mounted to the inlet duct leading to the turbocharger. The ECM uses the IAT information to control injection timing and fuel rate when starting cold. Engine Oil Temperature (EOT) Sensor The EOT sensor is mounted in the oil filter adapter. The EOT signal allows the ECM to compensate for viscosity changes in the oil due to temperature. The EOT signal is input into calculations that determine the fuel quantity and timing. 29 International ® VT 275 V6 Engine E D C B A