Electronic Engine Controls

The electronic engine controls consist of the:

• 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.
• power steering pressure (PSP) switch.
• mass air flow (MAF) sensor.
• heated oxygen sensor (HO2S).
• catalyst monitor sensor(s).
• knock sensor (KS).
• fuel rail pressure and temperature sensor.

The PCM:

• accepts input from various engine sensors to compute the fuel flow rate and spark timing necessary to maintain a prescribed air/fuel ratio throughout the entire engine operating range.
• outputs a command to the fuel injectors to meter the appropriate quantity of fuel.

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 at low engine speeds.
• accommodates for small changes in engine load.
• 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:

• provides camshaft position information which is used by the PCM for fuel synchronization.

The CKP sensor:

• sends the PCM a signal indicating crankshaft position.
• is essential for calculating spark timing.

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 additional load on the engine from the power steering pump.

The MAF sensor:

• uses a hot wire sensing element to measure the amount of air entering the engine.
• uses a second hot wire to measure intake air temperature.
• sends signals to the PCM. The PCM will then calculate the required fuel injector pulse width in order to provide the desired air/fuel ratio.

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 sensor(s):

• has the ability to create a voltage signal dependent on exhaust oxygen content.
• provides feedback information to the PCM used to calculate catalyst efficiency.

The KS:

• sends a signal to the PCM indicating engine detonation, which retards the ignition timing as necessary.

The fuel rail pressure and temperature sensor:

• measures the pressure and temperature of the fuel rail and sends these signals to the PCM.
• uses intake manifold vacuum as a pressure reference.