Fuel Injection System
INTRODUCTIONAll engines used have a sequential Multi-Port Electronic Fuel Injection system. The MPI system is computer regulated and provides precise air/fuel ratios for all driving conditions. The Power- train Control Module (PCM) operates the fuel injection system.
The PCM regulates:
- Ignition timing
- Air/fuel ratio
- Emission control devices
- Cooling fan
- Charging system Idle speed
- Vehicle speed control
Various sensors provide the inputs necessary for the PCM to correctly operate these Systems. In addition to the sensors, various switches also provide inputs to the PCM.
All inputs to the PCM are converted into signals. The PCM can adapt its programming to meet changing operating conditions.
Fuel is injected into the intake port above the intake valve in precise metered amounts through electrically operated injectors. The PCM fires the injectors in a specific sequence. Under most operating conditions, the PCM maintains an air fuel ratio of 14.7 parts air to 1 part fuel by constantly adjusting injector pulse width. Injector pulse width is the length of time the injector is open.
The PCM adjusts injector pulse width by opening and closing the ground path to the injector. Engine RPM (speed) and manifold absolute pressure (air density) are the primary inputs that determine injector pulse width.
SYSTEM DIAGNOSIS
The PCM can test many of its own input and output circuits. If the PCM senses a fault in a major system, the PCM stores a Diagnostic Trouble Code (DTC) in memory.
For DTC information, refer to Emission Control Systems. See On-Board Diagnostics.
Power Distribution Center (PDC):
POWER DISTRIBUTION CENTER
The Power Distribution Center (PDC) is located on the driver side of vehicle. The PDC contains the starter relay, radiator fan relay, A/C compressor clutch relay, auto shutdown relay, fuel pump relay and several fuses and other relays.
CCD BUS
Various modules exchange information through a communications port called the CCD Bus. The powertrain control module (PCM) transmits the Malfunction Indicator Lamp (Check Engine) On/Off signal and engine RPM on the CCD Bus. The PCM receives the Air Conditioning select input, transaxle gear position input and speed control engage inputs over the CCD Bus. The PCM also receives the air conditioning evaporator temperature signal from the CCD Bus.
The following components access or send information on the CCD Bus.
- Instrument Panel Cluster
- Body Control Module
- Air Bag System Diagnostic Module
- A/C Fin Sensor
- Transmission Control Module
- Powertrain Control Module