C 3500 HD Truck 2WD V8-8.1L VIN G (2002)
Alarm Module: Description and Operation
THEFT DETERRENT CONTROL MODULE - PASSLOCK(TM) MODULE
The theft deterrent control module - Passlock(TM) Module contains the logic of the theft deterrent system. The Passlock(TM) Module provides the
battery positive voltage to operate the Passlock(TM) sensor. The Passlock(TM) Module also measures the voltage of the security sensor signal circuit.
The voltage measured will indicate whether the Passlock(TM) sensor has been activated and whether the resistance value from the sensor is a valid value
or the tamper value. If voltage measured is in the valid range, the Passlock(TM) Module compares this voltage, voltage code, to a previously learned
voltage code. If the voltage codes match, the Passlock(TM) Module sends a class 2 message containing a password to the PCM. If the voltage codes do
not match, or the voltage is in the Tamper range, or there is a circuit fault, the Passlock(TM) Module will not send the correct password to the PCM, and
the vehicle will not start.
