C 3500 HD Truck 2WD V8-6.5L DSL Turbo VIN F (2001)
Engine Control Module: Description and Operation
Powertrain Control Module (PCM) Description
General Information
The Powertrain Control Module (PCM) processes the various input information. The PCM sends the necessary electrical responses to control fuel
delivery, spark timing, and other emission control systems. The input information has an interrelation to more than one output. One failed input can
affect more than one systems operation.
Diagnostic System Check-Computers and Control Systems
The Diagnostic System Check-Computers and Control Systems is an organized approach to identify a problem caused by an electronic engine control
system malfunction. The Diagnostic System Check-Computers and Control Systems must be the starting point for any driveability complaint diagnosis.
The Diagnostic System Check-Computers and Control Systems directs the technician to the next logical step in diagnosing the complaint.
Use the Engine Scan Tool Data Definitions list for a comparison after fulfilling the following items:
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Completes the Diagnostic System Check-Computers and Control Systems
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The on-board diagnostics are functioning properly
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Displays no diagnostic trouble codes
The Engine Scan Tool Definitions are an average of display values recorded from normal operating vehicles. The Definitions intend to represent what a
normal functioning system should display.
IMPORTANT: Do not use a scan tool that displays faulty data. Report the problem to the manufacturer. Using a malfunctioning scan tool can result in
misdiagnosis and unnecessary parts replacement.
Use only the parameters listed in the Engine Scan Tool Definitions for diagnosis. When a scan tool reads other parameters, General Motors recommends
not using the values for use in diagnosis.
For more description on the values and the use of the scan tool to diagnose the PCM inputs, refer to the applicable diagnostic file.
When all the values are within the range illustrated in the Engine Scan Tool Data Definitions, refer to Symptoms - Computers and Control Systems.
Control Module Communications
The control module system has a computer, the 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:
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Fuel control
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Fuel injection timing
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Exhaust Gas Recirculation (EGR)
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Transmission shift and shift quality functions
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Specific transmission control diagnostics are covered in Transmissions.
The diesel Powertrain Control Module (PCM), located in the passenger compartment, is the control center of the control module system. The powertrain
control module used on the electronic fuel injected 6.5L diesel is referred to as a PCM.
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. The PCM can recognize operational problems, alert the driver through the Malfunction Indicator Lamp (MIL) Service
Engine Soon, and store one or more Diagnostic Trouble Codes (DTCs) which identify the problem areas to aid the technician in making repairs. See the
specific diagnosis procedure for more information.
The PCM processes the various input information and sends the necessary electrical responses to control fuel delivery, timing and other emission control
systems. The input information has an interrelation 10 more than one output, therefore, if the one input failed it could effect more than one systems
operation.
Engine Controls Systems 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 Trouble Code (DTCs) tables:
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The component locations
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The wiring diagrams
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The control module terminal end view and terminal definitions
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The Diagnostic System Check-Computers and Control Systems
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The diagnostic trouble code (DTCs) tables
The component system includes the following items:
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The component and circuit description
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The on-vehicle service for each subsystem
