Electronic Engine Controls

The electronic engine controls consist of the following:

• powertrain control module (PCM)
• throttle position (TP) sensor
• idle air control (IAC) valve
• cylinder head temperature (CHT) sensor
• camshaft position (CMP) sensor
• crankshaft position (CKP) sensor
• mass air flow (MAF) sensor
• heated oxygen sensor (HO2S)
• catalyst monitor sensor
• vehicle speed sensor (VSS)
• intake manifold runner control (IMRC)

The PCM needs the following inputs to calibrate the engine correctly:

• crankshaft position
• intake air temperature
• engine load (manifold pressure)
• engine RPM
• engine coolant temperature
• camshaft position

The TP sensor:

• sends the PCM a signal indicating the throttle plate angle.
• is the main input to the PCM from the driver.

The IAC valve:

• controls bypass air around the throttle plate.
• is controlled by the PCM.

The CHT sensor:

• sends the PCM a signal indicating cylinder head temperature.
• resistance decreases as coolant temperature increases.

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 MAF sensor:

• sends the PCM a signal indicating the rate of mass air flow into the engine.

The IAT sensor:

• sends the PCM 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 PCM used to calculate fuel delivery.

The catalyst monitor sensors:

• monitor oxygen content after it flows through the catalytic converter.
• provides a voltage to the PCM used to calculate catalytic converter integrity.

The VSS:

• sends a signal to the PCM indicating wheel speed. For additional information, refer to AUTOMATIC TRANSAXLE/TRANSMISSION .

The air induction system improves engine performance by using the IMRC assemblies as follows:

• The lower intake manifold has 2 runners per cylinder, feeding each of the intake ports in the cylinder heads.
• The IMRC assemblies are located between the upper intake manifold and cylinder heads, providing 2 air passages for each cylinder.
• One air passage is always open and the other passage switches from closed to open by means of a valve plate.
  • Below 1,500 RPM, this valve plate is closed to improve fuel economy and emissions.
  • Above 1,500 RPM, this valve plate opens to improve high speed engine performance.

The valve plates are opened and closed by the IMRC electric actuator, which is controlled by the PCM.