Electronic Engine Control (EC) System

ELECTRONIC ENGINE CONTROLS

The electronic engine controls consist of the following:
- power control module (PCM)
- throttle position (TP) sensor
- idle air control (IAC) valve
- engine coolant temperature (ECT) sensor
- camshaft position (CMP) sensor
- fuel pump driver module
- fuel injection pressure and temperature sensor
- crankshaft position (CKP) sensor
- mass air flow (MAF) sensor
- intake air temperature (IAT) sensor
- heated oxygen sensor (HO2S)
- catalyst monitor sensor
- Knock sensor (KS) (4V)
- output shaft speed (OSS) sensor
- power steering pressure (PSP) switch (4V)

The PCM:
- accepts input from various engine sensors to compute the required fuel flow rate necessary to maintain a prescribed air/fuel ratio throughout the entire engine 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 in altitude (i.e. from sea level to above sea level).

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:
- is used to control engine idle speed.
- is controlled by the PCM.

The ECT sensor:
- sends the PCM a signal indicating engine temperature.
- resistance decreases as coolant temperature increases.

The CMP sensor:
- provides camshaft position information which is used by the PCM for fuel synchronization.

The fuel injection pressure and temperature sensor:
- measures the pressure and temperature of the fuel in the fuel supply manifold and sends these signals to the PCM.
- uses intake manifold vacuum as a pressure reference.

The fuel pump driver module:
- receives signals from the PCM.
- duty cycles the fuel pump.

The fuel pump relay engages the fuel pump when energized by the powertrain control module through the fuel pump driver module.

The CKP sensor:
- sends the PCM a signal indicating crankshaft position.
- is essential for calculating spark timing.

The KS 3.0L (4V)
- is used to detect engine detonation (spark knock).
- sends a voltage signal to the PCM which retards the ignition timing, as necessary.

The MAF sensor:
- uses a hot wire sensing element to measure the amount of air entering the engine.
- sends a signal to the PCM to determine the intake air mass. The PCM will then calculate the required fuel injector pulse width in order to provide the desired air/fuel ratio.

The catalyst monitor sensor:
- 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 HO2S:
- monitors oxygen content after it flows through the catalytic converter.
- provides a voltage to the PCM used to calculate catalytic converter integrity.

The PSP switch:
- is a normally closed switch that opens as pressure increases.
- is used to send a signal to the PCM to adjust idle speed. This compensates for the additional load on the engine.

The OSS:
- is able to provide a signal which tells the PCM the vehicle speed.