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.