Electronic Engine Controls

ELECTRONIC ENGINE CONTROLS

The electronic engine controls consist of the following:
- Camshaft position (CMP) sensor
- Crankshaft position (CKP) sensor
- Power steering pressure (PSP) switch
- Powertrain control module (PCM)
- Throttle position (TP) sensor
- Idle air control (IAC) valve
- Mass air flow (MAF) sensor
- Heated oxygen sensor (HO2S)
- Catalyst monitor sensor
- Cylinder head temperature (CHT) sensor
- Knock sensor (KS)
- Intake manifold runner control (IMRC)

The PCM needs the following inputs to calibrate the engine correctly:
- Crankshaft position
- Intake air temperature
- Engine load (manifold pressure)
- Engine rpm
- Engine coolant temperature
- Camshaft position

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 PSP switch:
- is a normally closed switch that opens as pressure increases.
- is used to send a signal to the PCM to adjust idle speed. This compensates for additional load on the engine from the power steering pump.

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.
- is controlled by the PCM.

The MAF sensor:
- sends the PCM a signal indicating the rate of mass air flow into the engine.

The HO2S:
- has the ability to create 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.
- provides a voltage to the PCM used to calculate catalytic converter integrity.

The CHT sensor:
- sends the PCM a signal indicating cylinder head temperature.
- resistance decreases as coolant temperature increases.

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 air induction system improves engine performance by using the IMRC assemblies as follows:
- The lower intake manifold has 2 runners per cylinder, feeding each of the intake ports in the cylinder heads.
- The IMRC assemblies are located between the upper intake manifold and 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.
- Below 1,500 rpm, this valve plate is closed to improve fuel economy and emissions.
- Above 1,500 rpm, this valve plate opens to improve high speed engine performance.

The valve plates are opened and closed by the IMRC electric actuator, which is controlled by the PCM.