General System Description
DESCRIPTIONThe control module system has a computer, Powertrain Control Module (PCM) to control fuel delivery, timing, and some emission control systems.
The control module system, monitors a number of engine and vehicle functions and controls the following operations:
^ Fuel control.
^ Fuel injection timing.
^ Exhaust gas recirculation.
^ Transmission shift and shift quality functions. Specific transmission control diagnostics are in Transmission Control Systems.
The PCM constantly looks at the information from various sensors, and controls the systems that affect vehicle performance. The PCM performs the diagnostic function of the system. It can recognize operational problems, alert the driver through the MIL (Service Engine Soon), and store one or more DTCs which identify the problem areas to aid the technician in making repairs.
OPERATION
The PCM is designed to process the various input information and then sends the necessary electrical responses to control fuel delivery, timing and other emission control systems. The input information has an interrelation to more than one output, therefore, if the one input failed it could effect more than one systems operation.
ENGINE CONTROLS INFORMATION
The driveability and emissions information describes the function and operation of the control module. The emphasis is placed on the diagnosis and repair of problems related to the system.
Engine Components, Wiring Diagrams, and Diagnostic Tables (DTCs):
^ Component Locations.
^ Wiring Diagrams.
^ Control Module Terminal End View and Terminal Definitions.
^ On-board Diagnostic (OBD) System Check.
^ Diagnostic Trouble Code Tables (DTCs).
The Component System includes the following items:
^ Component and circuit description
^ On-vehicle service for each sub-system
^ Functional checks and Diagnostic Tables
^ How To Use Electrical Systems Diagnostic information
The DTCs also contain diagnostic support information containing circuit diagrams, circuit or system information, and helpful diagnostic information.
MALFUNCTION INDICATOR LAMP (MIL)
The MIL (Malfunction Indicator Lamp) is on the instrument panel. The MIL has the following functions:
^ The MIL informs the driver that a fault that affects the vehicle's emission levels has occurred. The owner should take the vehicle for service as soon as possible.
^ As a bulb and system check, the MIL (Malfunction Indicator Lamp) comes on with the key on and the engine not running. When the engine is started, the MIL turns off if no DTCs are set.
When the MIL remains on while the engine is running, or when a malfunction is suspected due to a driveability or emissions problem, perform an On-Board Diagnostic (OBD) System Check. The procedures for these checks are given in engine controls. These checks expose faults which the technician may not detect if other diagnostics are performed first.
REPROGRAMMING (FLASHING) THE CONTROL MODULE
Some vehicles allow the reprogramming of the control module without any removal from the vehicle. This provides a flexible and a cost-effective method of making changes in the software and the calibrations. Refer to the latest Techline information on the reprogramming or the flashing procedures.
HIGH RESOLUTION SIGNAL (256X)
The high resolution signal is an optical device which generates 64 equally spaced pulses per cylinder combustion stroke from the slotted disc mounted on the injection pump timing cam ring. The pulses are counted by the PCM and are used in order to measure the angular pump displacement. The fuel is metered by using the angular indication. The timing is measured by counting the angular pulses between the pump cam signal and the crankshaft position sensor signal.