Electronic Engine Controls

ELECTRONIC ENGINE CONTROLS

The electronic engine controls consist of the:
- PCM.
- throttle position (TP) sensor.
- engine coolant temperature (ECT) sensor (4.0L SOHC).
- cylinder head temperature (CHT) sensor (4.6L [3V]).
- camshaft position (CMP) sensor.
- crankshaft position (CKP) sensor.
- mass air flow (MAF) sensor.
- heated oxygen sensor (HO2S).
- catalyst monitor sensor.
- knock sensor (KS).
- charge motion control valve (CMCV) (4.6L [3V]).
- variable camshaft timing (VCT) oil control solenoid (4.6L [3V]).

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.
- switches the PCV valve heat ON and OFF.

The TP sensor:
- sends the PCM a signal indicating the throttle plate angle.
- is the main input to the PCM from the driver.

The ECT sensor (4.0L SOHC):
- sends the PCM a signal indicating engine temperature.
- voltage decreases as coolant temperature increases.

The CHT sensor (4.6L 3V):
- is mounted to the wall of the cylinder head and is not connected to any coolant passages.

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 (4.0L SOHC only):
- 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.

The 4.6L (3V) air induction system improves engine performance by using the CMCV assemblies as follows:
- The intake manifold has 2 runners per cylinder, feeding each of the intake ports in the cylinder heads.
- The CMCV assemblies are located between the intake manifold and the cylinder heads, providing 2 air passages for each cylinder.
- One air passage is always open and the other passage switches from closed to open by means of a valve plate.
- The valve plates are opened and closed by the CMCV electric actuator, which is controlled by the PCM.

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.