The cass 2 serial data line communicates information between the modules. Each module connected to the serial data line is assigned a recognition code, or address. This code is used in order to identify which modules are communicating. The modules communicate with each other by periodically sending state of health (SOH) messages. When the ignition switch is in RUN, each module that is communicating on the serial data line sends an SOH message every 2 seconds. This ensures that the system is operating properly. When the key is turned on, most modules must learn the initialization data from other modules on the serial data line. When a module requests initialization data from another module, and that request is not acknowledged after 5 seconds, the module stores the cass 2 initialization error DTC U1255.
Wednesday, February 10th, 2010 AT 11:23 PM