C 3500 Truck 2WD V8-6.6L DSL Turbo VIN 1 (2002)
Engine Control Module: Description and Operation
Engine Control Module (ECM) Description
General Description
The Engine Control Module (ECM) processes the various input information. The ECM sends the necessary electrical responses to control fuel delivery.
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 Controls Systems
The Diagnostic System Check-Computers and Controls Systems is an organized approach to identify a problem caused by an electronic engine control
system malfunction. This diagnostic check must be the starting point for any driveability complaint diagnosis. The diagnostic 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:
^
Complete the Diagnostic System Check-Computers and Controls Systems.
^
Confirm that the on-board diagnostics are functioning properly.
^
Confirm there are 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 Data 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 ECM 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 Controls Systems.
Control Module Communications
The control module system has a computer, the Engine Control Module (ECM), 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 through the Fuel Injection Control
Module (FICM):
^
Fuel rail pressure
^
Fuel injector
^
Fuel injector pulse width
The diesel engine control module (ECM), located in the engine compartment, is the control center of the control module system. The engine control
module used on the electronic fuel injected 6.6L diesel is referred to as a ECM.
The ECM constantly looks at the information from various sensors, and controls the systems that affect vehicle performance. The ECM performs the
diagnostic function of the system. The ECM can recognize operational problems, alert the driver through the 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 ECM processes the various input information and sends the necessary electrical responses to control i!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 that input could effect more than
one systems operation.
Malfunction Indicator Lamp (MIL) Operation
