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
- Fuel rail pressure and temperature sensor
- Heated oxygen sensor (HO2S)
- Catalyst monitor sensor
- 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 4 fuel injectors at a time. The PCM will alternate which fuel injectors are disabled every 32 engine cycles. The 4 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 fuel rail pressure and temperature sensor:
- measures the pressure and temperature of the fuel rail and sends these signals to the PCM.
- uses intake manifold vacuum as a pressure reference.

The 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 catalyst monitor sensor(s):
- have the ability to create a voltage signal dependent on exhaust oxygen content.
- provide 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.