Data Sensors

The sensors consist of the manifold air temperature sensor (MAT), engine coolant temperature sensor, barometric pressure sensor (BARO), vehicle speed sensor (VSS), throttle position sensor (TPS) and engine speed sensor, which is provided by pulses from the EST distributor.
The manifold air temperature (MAT) sensor is installed in the intake manifold in front of the throttle body. This sensor measures the temperature of the fuel/air mixture in the intake manifold and provides this information to the ECM. The sensor is a thermistor whose resistance changes as a function of temperature. Low temperature provides high resistance and as temperature increases sensor resistance decreases.
The coolant temperature sensor is similar in function to the MAT sensor and is usually installed in the right front corner of the engine directly below the thermostat. This sensor provides data to the ECM for fuel enrichment during cold operation, for idle speed control, ignition timing and EGR operation.
The manifold absolute pressure (MAP) sensor monitors the changes in intake manifold pressure which result from engine load and speed changes. These pressure changes are supplied to the ECM in the form of electrical signals. As intake manifold pressure increases, additional fuel is required. The MAP sensor sends this information to the ECM so the injector ON time (or pulse width) will be increased.
Conversely as manifold pressure decreases, the pulse width will be shortened. The MAP sensor is mounted under the instrument panel near the righthand A/C outlet and is connected electrically to the ECM. A hose from the throttle body provides a vacuum signal to the sensor.
The barometric pressure sensor (BARO) senses ambient or barometric pressure and provides information to the ECM on ambient pressure changes due to altitude and/or weather. The sensor is mounted under the instrument panel near the right hand A/C outlet and is electrically connected to the ECM.
The vehicle speed sensor (VSS) informs the ECM as to how fast the vehicle is being operated. The ECM uses this information to determine the logic required to operate the fuel economy data panel (if applicable), cruise control and idle speed control system. A speed sensor buffer is positioned between the speed sensor and the ECM to amplify the weak signal generated by the sensor. The speed sensor and buffer are located behind the speedometer cluster.
The Throttle Position Sensor is a variable resistor mounted to the throttle body and is connected to the throttle valve shaft. Movement of the accelerator causes the throttle shaft to rotate (opening or closing the throttle blades). The sensor determines shaft position and transmits an appropriate electrical signal to the ECM. The ECM processes these signals to determine conditions for the idle speed control system.
The engine speed signal is originated from the electronic module in the EST distributor. Pulses from the distributor are sent to the ECM where the time between these pulses is used to calculate engine speed and spark advance.