Components

ELECTRONIC ENGINE CONTROLS

The electronic engine controls consist of the:
- powertrain control module (PCM).
- throttle position (TP) sensor.
- idle air control (IAC) valve.
- engine coolant temperature (ECT) sensor.
- camshaft position (CMP) sensor.
- crankshaft position (CKP) sensor.
- mass air flow (MAF) sensor.
- heated oxygen sensor (HO2S).
- catalyst monitor sensor.
- knock sensor (KS).

The PCM carries out the following functions:
- accepts input from various engine sensors to compute the fuel flow rate necessary to maintain a prescribed air/fuel ratio and spark synchronization 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 speeds.
- is controlled by the PCM.

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

The CMP sensor:
- sends the PCM a signal indicating camshaft position used for fuel and spark synchronization.

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

The MAF sensor:
- uses a hot wire sensing element to measure the amount of air entering the engine. Air passing over the hot wire causes it to cool.

The front HO2S:
- creates a voltage signal dependent on exhaust oxygen content.
- provides feedback information to the PCM used to calculate fuel delivery.

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

The KS:
- is used to detect engine detonation.
- sends a voltage signal to the PCM.
- is able to provide a signal which retards the ignition timing, as necessary.