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 rail 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 (such as, 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.