j894
09-05-06, 02:35 AM
http://www.gm.com/company/gmability/safety/images/safety_securityphoto.gif
Passlock? What is it ?
Passlock is an theft deterrent system introduced by GM in 1996, designed to prevent vehicle operation if the proper ignition key is not used to start the vehicle (passlock wasnt used in s-series until the '98 model). The Passlock Anti-Theft system involves resistor codes which are generated by resistors located in the ignition key cylinder switch.
In normal operation, the key turns the ignition lock cylinder. The Passlock sensor monitors the position of the lock cylinder and relays an analog Passlock signal to the body control module (BCM). The BCM determines the validity of the Passlock signal, then sends a password to the powertrain control module (PCM). When the PCM receives the correct password, it allows the fuel injectors to operate and the vehicle starts normally. Passlock communication between the PCM and BCM takes place over the Class 2 serial data line.
The Passlock sensor contains two Hall effect sensors. The security sensor is mounted under the tamper sensor. This arrangement enables the tamper sensor to engage first in the event a thief attempts to bypass the Passlock sensor by placing a large magnet around the area of the steering column.
A security resistor inside the Passlock sensor provides further theft protection. Ten different security resistors are available. Each generates a unique Passlock code that must be recognized by the BCM during a starting attempt. If the Passlock sensor, BCM or PCM are replaced, a relearn sequence must be followed to acquaint the new parts with each other and allow normal starting.
Depending on the model of GM vehicle, the actual resistor code is only introduced to the Passlock system when the ignition switch is turned to the ignition on (run) position or only when the ignition switch is turned to the start (crank) position.
Hope this helps understand passlock a little bit.
I compiled this from a few different sites/articles I found, let me know if anyone has additions/corrections,
info links:
http://www.gm.com/company/gmability/safety/security/theft_deterrence/index.html
http://www.madsci.org/posts/archives/may99/926999832.Eg.r.html
From:
http://www.findarticles.com/p/articles/mi_qa3828/is_200511/ai_n15871185
http://www.bulldogsecurity.com/pdf/Model721.pdf
http://townhall-talk.edmunds.com/direct/view/.ee95147/2641
Passlock? What is it ?
Passlock is an theft deterrent system introduced by GM in 1996, designed to prevent vehicle operation if the proper ignition key is not used to start the vehicle (passlock wasnt used in s-series until the '98 model). The Passlock Anti-Theft system involves resistor codes which are generated by resistors located in the ignition key cylinder switch.
In normal operation, the key turns the ignition lock cylinder. The Passlock sensor monitors the position of the lock cylinder and relays an analog Passlock signal to the body control module (BCM). The BCM determines the validity of the Passlock signal, then sends a password to the powertrain control module (PCM). When the PCM receives the correct password, it allows the fuel injectors to operate and the vehicle starts normally. Passlock communication between the PCM and BCM takes place over the Class 2 serial data line.
The Passlock sensor contains two Hall effect sensors. The security sensor is mounted under the tamper sensor. This arrangement enables the tamper sensor to engage first in the event a thief attempts to bypass the Passlock sensor by placing a large magnet around the area of the steering column.
A security resistor inside the Passlock sensor provides further theft protection. Ten different security resistors are available. Each generates a unique Passlock code that must be recognized by the BCM during a starting attempt. If the Passlock sensor, BCM or PCM are replaced, a relearn sequence must be followed to acquaint the new parts with each other and allow normal starting.
Depending on the model of GM vehicle, the actual resistor code is only introduced to the Passlock system when the ignition switch is turned to the ignition on (run) position or only when the ignition switch is turned to the start (crank) position.
Hope this helps understand passlock a little bit.
I compiled this from a few different sites/articles I found, let me know if anyone has additions/corrections,
info links:
http://www.gm.com/company/gmability/safety/security/theft_deterrence/index.html
http://www.madsci.org/posts/archives/may99/926999832.Eg.r.html
From:
http://www.findarticles.com/p/articles/mi_qa3828/is_200511/ai_n15871185
http://www.bulldogsecurity.com/pdf/Model721.pdf
http://townhall-talk.edmunds.com/direct/view/.ee95147/2641