Computers and Control Systems: Description and Operation

The electronic engine controls consist of the following:
^ Powertrain Control Module (PCM)
^ Throttle Position (TP) sensor
^ Idle Air Control valve (IAC)
^ Engine Coolant Temperature (ECT) sensor
^ Camshaft Position (CMP) sensor
^ Crankshaft Position (CKP) sensor
^ Mass Air Flow (MAF) sensor
^ Intake Air Temperature (IAT) sensor
^ Heated Oxygen sensor (HO2S)- front
^ Heated Oxygen sensor - rear
^ Knock Sensor
^ Vehicle Speed Sensor (VSS)
^ Engine Water Temperature sensor
^ Cylinder Head Temperature (CHT) sensor

The Powertrain Control Module needs the following inputs to calibrate the engine properly:
^ camshaft position
^ engine rpm
^ engine load (manifold pressure)
^ atmospheric (barometric) pressure
^ engine coolant temperature
^ amount of engine detonation

The Throttle Position sensor:
^ sends the powertrain control module a signal indicating the throttle plate angle.
^ is the main input to the powertrain control module from the driver.

The Idle Air Control valve:
^ controls bypass air around the throttle plate at low speeds.
^ is controlled by the Powertrain Control Module.

The Engine Coolant Temperature sensor:
^ sends the powertrain control module a signal indicating engine temperature.
^ resistance decreases as coolant temperature increases.

The Camshaft Position sensor:
^ sends the powertrain control module a signal indicating camshaft position used for fuel synchronization.

The Crankshaft Position sensor:
^ sends the powertrain control module a signal indicating crankshaft position.
^ is essential for calculating spark timing.

The Mass Air Flow sensor:
^ sends the powertrain control module a signal indicating mass air flow rate of air entering the engine.

The Intake Air Temperature sensor:
^ sends the powertrain control module a signal indicating the temperature of the air entering the engine.
^ resistance decreases as temperature increases.

The Heated Oxygen sensor:
^ has the ability to create a voltage signal dependent on exhaust oxygen content.
^ provides feedback information to the powertrain control module used to calculate fuel delivery.

The rear heated oxygen sensors:
^ monitor oxygen content after it flows through the catalytic converter.
^ provide a voltage to the Powertrain Control Module used to calculate catalytic converter integrity.

The Knock Sensor:
^ is located on the right side of engine block
^ sends a signal to the Powertrain Control Module indicating engine detonation.
^ if detonation is occurring, the powertrain control module then changes engine timing.

The Cylinder Head Temperature (CHT) sensor:
^ is mounted into the back of the left cylinder head and is not connected to any coolant passages.
^ sends a signal to the powertrain control module indicating the cylinder head temperature.
- If the temperature exceeds approximately 121 °C (260°F), the powertrain control module disables some fuel injectors. The powertrain control module will alternate which fuel injectors are disabled every 24 engine cycles. The cylinders that are not being fuel injected act as air pumps to aid in cooling the engine.
- If the temperature exceeds approximately 166°C (330°F), the powertrain control module disables all of the fuel injectors until the engine temperature drops below approximately 124°C (260°F).
^ DTCs are set.
^ If the engine reaches critical temperature, the following happens:
- The coolant temperature gauge pointer will read fully hot at approximately 121°C (260°F).
- The check gauge warning indicator will illuminate.

The Vehicle Speed sensor:
^ is gear driven by the transmission.
^ sends a signal to the powertrain control module indicating transmission output shaft speed.

The Intake Manifold Runner Control (IMRC) actuator:
^ is used only in this engine.
^ opens and closes the valve plates.
^ pushes the valve plates open above 3500 rpm.
^ closes the valve plates below 3500 rpm.