Suburban 1/2 Ton 2WD V8-5.3L VIN T (2004)
Engine Control Module: Description and Operation
Theft Deterrent
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.
