5.0L (MFI)

OPERATION
The engine control system includes a Powertrain Control Module (PCM)that receives inputs from various sensors. The PCM uses this information to control fuel flow, Exhaust Gas Recirculation (EGR), ignition, transmission controls for vehicles equipped with 4R70W transmission and evaporative emissions. These systems and the PCM work together to provide improved fuel economy, performance and lower exhaust emissions.

SUBSYSTEMS AND COMPONENTS

PCM Power Relay
The PCM power relay supplies power to the PCM and PCM system-related components. When the ignition switch is turned to "RUN" or "START" voltage is applied to the PCM power relay coil, closing the relay's contacts.

Voltage is applied to the fuel pump relay, fuel injectors, PCM, EGR solenoid and secondary air injector solenoids, through the PCM power relay contacts.

Fuel Flow
The Multiport Fuel Injection (MFI) system uses fuel injectors mounted in the intake manifold at the intake port to meter fuel into the engine.

The fuel injectors are divided into two groups of four. With each crankshaft revolution, one group is energized. The next crankshaft revolution energizes the second group of injectors.

The PCM controls the length of time that the injectors are energized (injector on time" or pulse width). It also determines the appropriate injector pulse width and outputs a command to the injector to meter the exact quantity of fuel.

The electric fuel pump supplies fuel under pressure to the fuel rail and the fuel injectors. When the ignition switch is in "RUN" or "START", voltage is applied from the PCM power relay to the fuel pump relay coil. The coil is grounded by the PCM and the relay contacts close. Voltage is now applied to the electric fuel pump.

The inertia fuel shutoff is a safety device that cuts voltage to the electric fuel pump if a collision occurs. Once the switch opens it must be reset manually.

Exhaust Gas Recirculation (EGR)
The PCM controls exhaust gas recirculation by varying the duty cycle signal applied to the EGR solenoid. This solenoid regulates the amount of vacuum applied to the EGR Valve. The EGR valve position sensor indicates valve position to the PCM by providing a voltage signal proportional to the EGR position (depending on engine operating conditions).

Idle Air Control (IAC) Valve
The idle air control valve controls idle speed during all modes of engine operation. The idle air control valve receives duty cycle signals from the PCM which controls a solenoid which opens or closes the air bypass passage depending on the signal received. The valve will close as the signal from the PCM stops.

Intake Air Temperature (IAT) Sensor
The Intake air temperature sensor is a thermistor whose resistance decreases as intake air temperature increases. The PCM measures the voltage drop across the Intake Air Temperature Sensor and uses this information to help calculate fuel delivery, spark timing and EGR control.

Throttle Position (TP) Sensor
The throttle position sensor is a potentiometer with a DC voltage output that varies with throttle plate angle. By monitoring the throttle position sensor output, the PCM calculates fuel delivery requirements based on driver demand.

Engine Coolant Temperature (ECT) Sensor
The engine coolant temperature sensor is a thermistor in which resistance decreases as engine coolant temperature increases. The PCM measures the voltage drop across the engine coolant temperature sensor and uses this information to help calculate fuel delivery, spark timing and EGR control.

Heated Oxygen Sensor (HO2S)
The Heated Oxygen Sensor (HO2S) provides a voltage related to the oxygen content of the exhaust gases to the PCM for regulating the air/fuel ratio. Too much oxygen indicates a lean mixture, while too little oxygen indicates a rich mixture.

Ignition
The engine control system has a special distributor and ignition module. The distributor has no vacuum advance mechanism. Instead, all ignition timing is controlled by the PCM.

The PCM receives engine timing information from the distributor through the Ignition Control Module (ICM). The PCM uses this information to determine spark timing and advance.