Electronic Engine Controls

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 injection pressure and temperature sensor
- Crankshaft position (CKP) sensor
- Mass air flow (MAF) sensor
- Heated oxygen sensor (HO2S)
- Knock sensor (KS)

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

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