Passlock(tm) Sensor
The Passlock(tm) sensor is inside the ignition cylinder lock housing. The Passlock(tm) sensor contains 2 hall
effect sensors. The tamper hall effect sensor is on the top. The security hall effect sensor is under the tamper
hall effect sensor. Both of the hall effect sensors monitor the magnet of the lock cylinder through an opening.
The tamper hall effect sensor is physically placed on top of the security hall effect sensor. This arrangement
enables the tamper hall effect sensor to engage first if an intruder attempts to bypass the Passlock(tm) sensor by
placing a large magnet around that area of the steering column. There is a tamper resistor inside the Passlock
(tm) sensor in order to help prevent tamper to the system. Passlock(tm) equipped vehicles have a selection of 10
different security resistors ranging from 0.5K ohms up to 13.6K ohms. Installing one of the security resistors
inside the Passlock(tm) sensor will generate a unique Passlock(tm) code. All 10 combinations of the Passlock
(tm) sensor have the same part number. However, you cannot simply replace the Passlock(tm) sensor and
expect the system to operate properly. Always start by performing the Diagnostic System Check first and
following the instructions.
Body Control Module
The Body Control Module (BCM) contains the theft deterrent system logic. The BCM reads the Passlock(tm)
data from the Passlock(tm) sensor. If the Passlock(tm) data is correct, the BCM will pass theft. The BCM will
then transmit the fuel continue password to the VCM/PCM.
During the tamper mode the vehicle may start. The vehicle will then stall. If the BCM receives the wrong
Passlock(tm) data, the VTD will immediately go into the tamper mode. The tamper mode will lock-out the
vehicle fuel injectors for 10 minutes. The SECURITY indicator will flash while the VTD is in the tamper mode.
If the Passlock(tm) sensor sends a correct password to the BCM when the ignition is in the ON position, the
BCM will send a fuel enable signal to the VCM/PCM. The VCM/PCM will not disable the fuel due to any
BCM message for the remainder of the ignition cycle.
SECURITY Telltale
The SECURITY telltale appears on the message center inside the instrument cluster. If the SECURITY telltale
flashes or if the SECURITY telltale lights continuously during the vehicle operation, refer to the system
diagnosis.
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.
Fuel Lockout Cycle
2004 Hummer H2
2004 ACCESSORIES & EQUIPMENT Theft Deterrent - Hummer H2