Computers and Control Systems: Description and Operation

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

The Powertrain Control Module needs the following inputs to control the engine properly:
^ camshaft position.
^ engine rpm.
^ engine cylinder head 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 Camshaft Position sensor:
^ sends the powertrain control module a signal indicating camshaft position used for fuel synchronization and coil firing.

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 airflow rate of air entering the engine.

The Mass Air Flow (MAF) sensor:
^ sends the powertrain control module a signal indicating mass airflow 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 unique linear knock sensor is located top forward of the block under the intake manifold.
^ 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 wall of the 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 126°C (-258°F), the powertrain control module disables four fuel injectors at a time. The powertrain control module will alternate which four injectors are disabled every 32 engine cycles. The four cylinders that are not being fuel injected act as air pumps to aid in cooling the engine.
- if the temperature exceeds 154°C (310°F), the powertrain control module disables all of the fuel injectors until the engine temperature drops below 154°C (310°F).
^ DTCs are set.
^ If the engine reaches critical temperature, the following happens:
- The coolant temperature gauge pointer will read fully hot at 121°C (250°F).
- The check gauge warning indicator will illuminate.

The Clutch Pedal Position (CPP) switch:
^ sends a signal to the Powertrain Control Module indicating clutch pedal position.