GM Service Manual Online
For 1990-2009 cars only

The design of the passlockā„¢ system is to prevent the vehicle operation if the proper ignition key is not used in order to start the vehicle. The mechanical key, in normal operation, will turn the passlockā„¢ lock cylinder. The passlockā„¢ sensor will relay the passlockā„¢ data to theEVO/Passlockā„¢ module. The EVO/Passlockā„¢ module will determine the validity of the passlockā„¢ data. The EVO/Passlockā„¢ module will send a code password to the vehicle/powertrain control module (VCM/PCM). When the VCM/PCM receives the correct code the VCM/PCM allows the fuel injectors to operate normally. The passlockā„¢ system requires the VCM and the EVO/Passlockā„¢ module to communicate the various functions in order to operate. These functions transmit over the class 2 serial data line CKT 1807. For an explanation of the class 2 serial data operation refer to Data Link Communications Circuit Description in Data Link Communications