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 BE IGNITED, 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
- engine water temperature sensor

The powertrain control module needs the following inputs to calibrate the engine properly:
- crankshaft position
- engine rpm
- engine load (manifold pressure)
- atmospheric (barometric) pressure
- engine coolant temperature
- amount of engine detonation

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:
- provides a gauge signal for coolant temperature.
- is mounted on top of the intake manifold.

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 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.
- DTCs are set.
- 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 check gauge warning indicator will illuminate.

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