Electronic Engine Controls

The electronic engine controls consist of the following:

• powertrain control module (PCM)
• throttle position (TP) sensor
• idle air control (IAC) valve
• 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 (HO2S) - rear
• cylinder head temperature (CHT) sensor

The PCM carries out the following functions:

• accepts input from various engine sensors to complete the required fuel flow rate necessary to maintain a prescribed air/fuel ratio throughout the entire operational range.
• outputs a command to the fuel injectors to meter the appropriate quantity of fuel.
• determines and compensates for the age of the vehicle and its uniqueness, also automatically senses and compensates for changes in altitude.

The TP 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 IAC valve:

• controls bypass air around the throttle plate at low speeds.
• is controlled by the powertrain control module.

The CMP sensor:

• sends the powertrain control module a signal indicating camshaft position used for fuel synchronization.

The CKP sensor:

• sends the powertrain control module a signal indicating crankshaft position.
• is essential for calculating spark timing.
• sends the powertrain control module signals to indicate engine rpm.

The MAF sensor:

• sends the powertrain control module a signal indicating fresh air flow rate of air entering the engine.

The IAT sensor:

• sends the powertrain control module a signal indicating the temperature of the air entering the engine.
• resistance decreases as temperature increases.

The HO2S:

• 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 HO2S:

• monitors oxygen content after it flows through the catalytic converter.
• provides a voltage to the powertrain control module used to calculate catalytic converter integrity.

The 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 approximately 121°C (250°F), the powertrain control module disables four fuel injectors at a time. The powertrain control module will alternate which fuel 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 approximately 166°C (330°F), the powertrain control module disables all of the fuel injectors until the engine temperature drops below approximately 154°C (310°F).
• If the engine reaches critical temperature, the following happens:
  • The coolant temperature gauge pointer will read fully hot at approximately 121°C (250°F).