Class 2

Modules on the Class 2 data line use State of Health communication messages to control and monitor other modules. Some control modules on the Class 2 communication system have the ability to recognize other modules that are no longer communicating. When this problem occurs, the module(s) that recognize the problem may store one or more DTCs identifying the failed module. From the beginning of a power mode, communications between modules continues every 2 seconds. If the communication time between modules passes 5 seconds a State of Health DTC will set.

Failure to communicate with the Class 2 data circuit could be anyone of the following faults:
^ A faulty Class 2 data line, CKT 1807 (PPL)
^ A fault in the modules power circuit
^ A fault in modules ground circuits
^ A faulty control module

Communication failure DTCs are identified as 5 digit codes, with the first digit being U. The remaining digits are numeric and refer to the specific system that has failed.