Diagnostic System Check - Automatic Day - Night Mirror

A Diagnostic System Check - Automatic Day-Night Mirror:

TEST DESCRIPTION
The number(s) below refer to the step number(s) on the diagnostic table.
2. Lack of communication may be due to a partial malfunction of the class 2 serial data circuit or due to a total malfunction of the class 2 serial data circuit. The specified procedure will determine the particular condition.
4. The presence of DTCs which begin with ~U" indicate some of the modules are not communicating.