Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. 1.  A Lost Communication with XXX DTC with a history status may indicate the cause of U1000 or U1255.
2. 2.  The module which are not communicating will be the likely cause of U1000 or U1255 being set. For a list of the modules that communicate on the class 2 serial data circuit, refer to DATA LINK COMMUNICATIONS DESCRIPTION AND OPERATION 
3. 5.  The module which was not communicating may have set Lost Communication with XXX DTCs for those modules that it was monitoring.
4. 6.  The module which was not communicating may have set Lost Communication with XXX DTCs for those modules that it was monitoring.
5. 7.  The module which was not communicating may have set Lost Communication with XXX DTCs for those modules that it was monitoring.
6. 11.  The modules which can communicate indicate the module which cannot communicate. You must clear the DTC from these modules to avoid future misdiagnosis.
7. 13.  If all modules are communicating, the module which set U1000 or U1255 may have done so due to some other condition.
8. 14.  The module which set U1000 or U1255 is the likely cause of the malfunction.