Electronic Engine Controls

ELECTRONIC ENGINE CONTROLS

The electronic engine controls consist of the following:
- camshaft position (CMP) sensor
- crankshaft position (CKP) sensor
- cylinder head temperature (CHT) sensor
- engine coolant temperature (ECT) sensor
- heated oxygen sensor (HO2S) - front
- heated oxygen sensor (HO2S) - rear
- mass air flow (MAF) sensor
- powertrain control module (PCM)

The CMP sensor:
- sends the PCM a signal indicating camshaft position used for fuel synchronization.

The CKP sensor:
- sends the PCM a signal indicating crankshaft position.
- is essential for calculating spark timing.

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 PCM indicating the cylinder head temperature.
- If the temperature exceeds approximately 121°C (250°F), the PCM disables four fuel injectors at a time. The PCM 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 PCM 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).

The ECT sensor:
- sends the PCM a signal indicating crankshaft position.
- is essential for calculating spark timing.

The front HO2S:
- has the ability to create a voltage signal dependent on exhaust oxygen content.
- provides feedback information to the PCM used to calculate fuel delivery.

The rear HO2S:
- monitors oxygen content after it flows through the catalytic converter.
- provides a voltage to the PCM used to calculate catalytic converter integrity.

The MAF sensor:
- sends the PCM a signal indicating fresh air flow rate of air entering the engine.

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.