Computers and Control Systems: Description and Operation

Engine Coolant Temperature Sensor
The engine temperature sensor is located in the flow of the engine coolant and sends information concerning temperature to the ECM.

Oxygen Sensor
The exhaust oxygen sensor is located in the exhaust system and monitors oxygen content in the exhaust gas stream. The ECM receives this information and adjusts the air/fuel ratio as necessary.

Manifold Absolute Pressure Sensor
The manifold absolute pressure (MAP) sensor measures changes in the intake manifold pressure resulting from engine load and speed changes. As the pressure changes, the electrical resistance of the sensor changes. This change in resistance causes a voltage change which is amplified and sent to the ECM.

Vehicle Speed Sensor
The vehicle speed sensor (VSS) is located behind the speedometer in the instrument cluster. The sensor sends a series of pulses to the ECM used to determine road speed. The ECM uses this information to reset the idle air control motor, canister purge and [1][2]torque converter clutch. Do not drive vehicle without VSS, as idle quality may be affected.

Throttle Position Sensor
The throttle position sensor (TPS) is connected to the throttle shaft and is controlled by the throttle mechanism. The TPS converts the throttle valve angle to an electrical signal and transmits the signal to the ECM.

Hall Effect Unit
The Hall Effect Unit is located above the pickup coil in the distributor and sends engine RPM information to the ECM. This unit is used in place of the ``R'' terminal of the conventional HEI module.

Park/Neutral Switch
The park/neutral switch indicates to the ECM when the transmission is in park or neutral. Do not drive vehicle with park/neutral switch disconnected, as idle quality may be affected in park or neutral.

A/C Compressor Clutch Engagement
The A/C compressor clutch engagement signal tells the ECM that the A/C compressor clutch is engaged.