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.