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. For additional information, refer to POWER STEERING .

The OSS:

• is able to provide a signal which tells the PCM the vehicle speed. For additional information, refer to AUTOMATIC TRANSAXLE/TRANSMISSION - 4F50N .