K 1500 Suburban 4WD V8-5.3L VIN Z Flex Fuel (2003)
Engine Control Module: Description and Operation
Vehicle/Powertrain Control Module
VEHICLE/POWERTRAIN CONTROL MODULE
The VCM/PCM communicates with the BCM over the Class 2 serial data line. When the BCM determines a no start condition, it sends a Class 2
serial data password to the VCM/PCM in order to disable the fuel injection system. If the BCM receives the expected voltage from the Passlock(TM)
sensor, the BCM sends a class 2 serial data password to the VCM/PCM in order to enable the fuel injection system. The VCM/PCM then allows the
vehicle to start correctly. If the Class 2 serial data password from the BCM to the VCM/PCM is not within the Vehicle Security Status Message, the
fuel injectors will shut OFF during a start attempt. The SECURITY telltale will be illuminated for 10 minutes. If the VCM/PCM does not receive the
same password from the BCM as the last learned one, the vehicle will start and then stalls due to the Fuel Lockout.
The PCM verifies that the password received from the theft deterrent control module via the serial data circuit is correct. The PCM can learn only one
fuel continue password. If the fuel continue password is correct, the PCM enables the starting and fuel delivery systems.
The PCM disables the starting and fuel delivery systems if any of the following conditions occur:
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The fuel continue password is incorrect.
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The fuel disable password is sent by the theft deterrent control module.
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No passwords are received - there is no communication with the theft deterrent control module.
