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Home >> Mazda >> 1993 >> B Series Truck 2WD L4-2184cc 2.2L 2200 2-bbl >> Repair and Diagnosis >> Powertrain Management >> Computers and Control Systems >> Description and Operation >> General System Description >> Fuel Injection
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Fuel Injection

System Description:






The Powertrain Control Module (PCM) is the central component of this computerized fuel, ignition and emission control system. To maintain fuel economy, good driveability and reduced vehicle emissions, the PCM monitors data from various sensors and controls functions such as the fuel injection system (air/fuel ratio), emission control devices and on-board diagnostics.

The PCM is a computer that judges air/fuel ratio as rich or lean according to a voltage signal generated by an oxygen sensor. Based on oxygen sensor and other input data, the PCM generates a controlling signal to the fuel injectors that regulates "ON" time. Because fuel pressure remains constant, the PCM controls air/fuel ratio adjustments by varying injector "ON" time.

To provide a margin of safety by maintaining driveability in the event of certain system failures, the PCM has a fail-safe mode of preprogrammed values. The output of the PCM will automatically switch to fail-safe mode if a fault is detected in any of these components and/or systems:

^ Airflow meter
^ Barometric absolute pressure sensor
^ Feedback system
^ Intake air temperature sensor
^ Oxygen sensor
^ Throttle sensor
^ Engine coolant temperature sensor

The system incorporates self-diagnostic capability monitored via a dash mounted malfunction indicator lamp (MIL). When the system detects a fault in a monitored component and/or circuit, the lamp will light ("CHECK") and stay on (while the engine is running), alerting the driver to seek service. The technician can then extract trouble codes from the PCM to aid in troubleshooting and repair.

Components can be grouped as PCM input and output devices. Input devices control or produce voltage signals monitored by the PCM. Output devices are components controlled by the PCM. Not all of these devices are monitored by the on-board diagnostic system.

INPUT DEVICES
^ A/C switch
^ Airflow meter (code 08)
^ Barometric absolute pressure sensor (code 14)
^ Distributor
-G signal (code 03)
-Ne signal (code 02)
^ Electrical load signal
^ Feedback system (code 17)
^ Idle switch
^ Ignition switch ("START" and "ON" positions)
^ Park/neutral switch (A/T)
^ Intake air temperature sensor (code 11)
^ Neutral and clutch switches (M/T)
^ Oxygen sensor (code 15)
^ Power steering pressure switch
^ Stop light switch
^ Test connector
^ Throttle sensor (code 12)
^ Engine coolant temperature sensor (code 09)

OUTPUT DEVICES
^ A/C relay/cut-off
^ Burn-off control system
^ Bypass air control (BAC) valve
-Air valve
-Idle air control valve (code 34)
^ Circuit opening relay (fuel pump control)
^ Fuel injectors/injection timing
^ Igniter
^ Malfunction indicator lamp (MIL)
^ Pressure regulator solenoid valve (code 25)
^ Purge control solenoid valve (code 26)
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