K 2500 Truck 4WD V8-6.5L DSL Turbo VIN S (1998)
Powertrain Control Module (PCM): Description and Operation
POWERTRAIN CONTROL MODULE DESCRIPTION
The PCM processes the various input information. The PCM sends the necessary electrical responses to the 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 system's
operation.
ON-BOARD DIAGNOSTIC SYSTEM CHECK
The On-Board Diagnostic (OBD) System Check is an organized approach to identify a problem caused by an electronic engine control system
malfunction. The OBD must be the starting point for any driveability complaint diagnosis. The OBD 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 OBD System Check
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The on-board diagnostics are functioning properly
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Displays no diagnostic trouble codes
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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.
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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.
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For more description on the values and the use of the scan tool to diagnose the PCM inputs, refer to the applicable diagnostic file.
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When all the values are within the ranged illustrated in the Engine Scan Tool Data Definitions, refer to Driveability Symptoms. See: Testing and
Inspection
CONTROL MODULE COMMUNICATIONS
The 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:
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Fuel control.
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Fuel injection timing.
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Exhaust gas recirculation.
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Transmission shift and shift quality functions.
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Specific transmission control diagnostics are covered in Transmissions.
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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.
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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. See the specific diagnosis procedure for more information.
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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 to more than one output, therefore, if the one input failed it could effect more than one
systems operation.
AFTERMARKET (ADD-ON) ELECTRICAL AND VACUUM EQUIPMENT
Installed any equipment on a vehicle after leaving the factory that connects to the electrical or vacuum systems of the vehicle defines Aftermarket
(Add-On) Electrical and Vacuum Equipment. The vehicle design makes no allowances for this type of equipment.
IMPORTANT NOTES:
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Do not attach add-on vacuum operated equipment to this vehicle. The use of add-on vacuum equipment may result in damage to vehicle
components or systems.
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Connect any add-on electrically operated equipment to the vehicle's electrical system at the battery (power and ground) in order to prevent
damage to the vehicle.
The Add-On electrical equipment, even when installed to these strict guidelines, may still cause the Powertrain system to malfunction. This may also
