Computers and Control Systems: Description and Operation

WARNING: DO NOT SMOKE, CARRY LIGHTED TOBACCO, OR OPEN FLAME OF ANY TYPE WHEN WORKING ON OR NEAR ANY FUEL RELATED COMPONENT. HIGHLY FLAMMABLE MIXTURES ARE ALWAYS PRESENT AND MAY IGNITE, RESULTING IN POSSIBLE PERSONAL INJURY.

The electronic engine controls consist of the following:
- powertrain control module
- throttle position sensor
- idle air control valve
- engine coolant temperature sensor
- camshaft position sensor
- crankshaft position sensor
- mass air flow sensor
- intake air temperature sensor.
- heated oxygen sensor-front
- heated oxygen sensor-rear
- wheel speed sensor

The powertrain control module needs the following inputs to calibrate the engine correctly:
- crankshaft position
- intake air temperature
- intake mass air flow
- engine rpm
- engine coolant temperature

The throttle position 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 idle air control valve:
- controls bypass air around the throttle plate at low speeds.
- is controlled by the powertrain control module.

The engine coolant temperature sensor:
- sends the powertrain control module a signal indicating engine temperature.
- resistance decreases as coolant temperature increases.

The camshaft position sensor:
- sends the powertrain control module a signal indicating camshaft position used for fuel synchronization.

The crankshaft position sensor:
- sends the powertrain control module a signal indicating crankshaft position.
- is essential for calculating spark timing. The mass air flow sensor:
- sends the powertrain control module a signal indicating mass air flow rate of air entering the engine.

The intake air temperature sensor:
- sends the powertrain control module a signal indicating the temperature of the air entering the engine.
- a resistance decreases as temperature increases.

The front heated oxygen sensor:
- 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 heated oxygen sensor:
- 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 wheel speed sensor:
- sends a signal to the powertrain control module indicating wheel speed.

The air induction system improves engine performance by using the Intake Manifold Runner Control (IMRC) assemblies as follows:
- The lower intake manifold has two 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 two 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 2450 rpm, this valve plate is closed to improve fuel economy and emissions.
- Above 2450 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 powertrain module.