Powertrain Control Module (PCM)
DESCRIPTION AND OPERATION
The Control Module refers to the Powertrain Control Module (PCM). The control module is designed to maintain exhaust emission levels to Federal or California standards while providing excellent driveability and fuel efficiency. Review the components and wiring diagrams in order to determine which systems are controlled by each specific control module. The control module monitors numerous engine and vehicle functions. The control module controls the following operations:
^ Fuel control
^ Ignition Control (IC)
^ Knock Sensor (KS) system
^ Automatic transmission shift functions
^ Cruise Control Enable
^ Generator
^ Evaporative Emission (EVAP) Purge
^ A/C Clutch Control
^ Cooling Fan Control
CONTROL MODULE FUNCTION
The Control Module supplies a buffered voltage to various sensors and switches. The input and output devices in the control module include an analog to digital converters, signal buffers, counters, and special drivers. The Control Module controls most components with electronic switches which complete a ground circuit when turned ON. These switches are arranged in groups of 4 and 7 called one of the following:
^ Quad Driver Module
^ Output Driver Modules
The surface mounted Quad Driver Module can independently control up to 4 outputs (Control Module) terminals. The Output Driver Modules can independently control up to 7 outputs. Not all outputs are always used.
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):
^ The Component Locations
^ The Wiring Diagrams
^ The Control Module Terminal End View and Terminal Definitions
^ The On Board Diagnostic (OBD) System Check
^ The Diagnostic Trouble Code Tables (DTCs)
The Component System includes the following items:
^ The Component and circuit description
^ The On-vehicle service for each sub-system
^ The Functional checks with the Diagnostic Tables
^ How To Use Electrical Systems Diagnostic Information
The DTCs also contain the diagnostic support information containing the circuit diagrams, the circuit or the system information, and helpful diagnostic information. Refer to Computers and Controls / Testing and Inspection.