Electronic Engine Controls: Notes

The 3.7L electronic engine controls consist of the:

• PCM.
• Cylinder Head Temperature (CHT) sensor.
• Camshaft Position (CMP) sensor.
• Crankshaft Position (CKP) sensor.
• Mass Air Flow (MAF) sensor.
• Heated Oxygen Sensor (HO2S).
• Catalyst Monitor Sensor (CMS).
• Variable Camshaft Timing (VCT) oil control solenoid.
• Knock Sensor (KS).

The PCM:

• 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 cylinder head temperature increases.

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 CMS :

• monitors oxygen content after it flows through the catalytic converter.
• provides a voltage to the PCM used to calculate catalytic converter integrity.

The VCT oil control solenoid:

• is an electrically controlled hydraulic valve that directs engine oil to the variable camshaft. Once the PCM transmits a signal, the solenoid moves a valve spool, directing oil into the camshaft phaser cavity. This action changes valve timing by either inducing an advance or retard condition. The camshaft is, thereby repositioned in relation to crankshaft timing and allows for optimum engine performance and lower emissions.

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.