C 3500 HD Truck 2WD V8-6.5L DSL Turbo VIN F (2001)
Engine Control Module: Description and Operation
Vehicle Theft Deterrent (VTD) Description And Operation
The PCM communicates with the passlock module over the Class 2 serial data line. When the passlock module determines a no start condition, it sends a
Class 2 serial data password to the PCM in order to disable the fuel injection system. If the passlock module receives the expected voltage from the
Passlock(TM) sensor, the passlock module sends a class 2 serial data password to the PCM in order to enable the fuel injection system. The PCM then
allows the vehicle to start correctly. If the Class 2 serial data password from the passlock module to the 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 PCM does not receive
the same password from the passlock module as the last learned one, the vehicle will start and then stalls due to the Fuel Lockout.
