Electronic Engine Controls

The electronic engine controls consist of the following:

• Powertrain control module (PCM)
• Cylinder head temperature (CHT) sensor
• Throttle position (TP) sensor
• Idle air control (IAC) valve
• 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 throughout the entire engine operational range.
• outputs a command to the fuel injectors to meter the appropriate quantity of fuel.

The CHT sensor:

• sends the PCM a signal indicating cylinder head temperature.
• resistance decreases as coolant temperature increases.

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 CMP sensor:

• sends the PCM a signal indicating camshaft position used for fuel 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 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.