Electronic Engine Controls

ELECTRONIC ENGINE CONTROLS

The electronic engine controls consist of the following:
- powertrain control module (PCM).
- throttle position (TP) sensor.
- cylinder head temperature (CHT) sensor.
- camshaft position (CMP) sensor.
- crankshaft position (CKP) sensor.
- mass air flow (MAF) sensor.
- heated oxygen sensors (HO2S).
- catalyst monitor sensors.
- knock sensor (KS).
- intake manifold tuning (IMT) valve.

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 TP sensor:
- sends the PCM a signal indicating the throttle plate angle.
- is the main input to the PCM from the driver.
- is serviced as part of the throttle body.

The CHT sensor:
- is mounted into the wall of the cylinder head and is not connected to any coolant passages.
- sends the PCM a signal indicating cylinder head temperature.
- if the temperature exceeds approximately 121°C (250°F), the PCM disables half of the fuel injectors at a time. The PCM will alternate which fuel injectors are disabled every 32 engine cycles. The cylinders that are not being fuel injected act as air pumps to aid in engine cooling.
- If the temperature exceeds approximately 166°C (330°F), the PCM disables all of the fuel injectors until the engine temperature drops below approximately 154°C (310°F).
- The coolant temperature gauge pointer will read fully hot.
- The check gauge warning indicator will illuminate and DTCs are set.

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 sensors:
- monitor oxygen content after it flows through the catalytic converter.
- provide 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.

The IMT:
- improves the upper rpm power.