Powertrain Management: Description and Operation

PGM-FI System Description:

PURPOSE
This vehicle is equipped with a Programmed Fuel Injection (PGM-FI) sequential multiport fuel injection system. This system uses sensor inputs to the Engine Control Module (ECM) to control engine fuel injector timing and duration, fuel pumping, idle speed, and spark timing. In addition, on automatic transmission equipped vehicles, the engine and transmission control functions are combined into a Powertrain Control Module (PCM) which uses the engine control information to determine shift timing and torque converter clutch lock-up.


OPERATION
Under cold start conditions, the ECM increases fuel injection duration, and provides additional air to the intake manifold for proper cold operation. During warm-up and at operating temperature, engine sensors feed information on engine conditions, climatic conditions, and road speed to the ECM. This information is used to determine which of the pre-programmed "maps" in the ECM memory will be followed. These maps outline exactly when and for how long the fuel injectors are open, and when the spark plugs fire. At idle, the ECM directs the idle air system to introduce additional air into the intake system to maintain proper idle speed with changes in engine load (including air conditioning compressor "ON," power steering use, alternator charging, automatic transmission in gear). The ECM also monitors electrical loads and driving modes and determines alternator voltage generation. If any abnormality occurs in the PGM-FI system, the ECM has the ability to: ignore a faulty sensor, store codes associated with a failure of a sensor or other component, and, provide continued operation during most failures. If the failure is internal to the ECM (or the PCM) itself, a back-up mode allows minimal driving in most failure modes.



CONSTRUCTION
The ECM (and PCM) circuitry are contained in housings constructed of cast aluminum and steel stampings, mounted on a steel plate at the passengers side of the firewall. They are interconnected to the sensors, actuators and other PGM-FI components under the hood via a main harness with quick disconnect pin-type connectors at all connections. Fuses to protect the system are found in both the under-dash and under-hood fuse boxes.