Class 2 Data Line

Modules on the class 2 data line transmit state of health messages every two seconds to indicate proper functioning to other modules on the data line. Some modules recognize when other modules are not communicating. A Diagnostic Trouble Code (DTC) may be stored by a module that detects five seconds of non-communication from another module. Data line DTCs begin with the letter "U" and may be caused by faulty data line wiring, faulty module power or ground or a faulty control module.