GM repair charts are organized by section in their GM publications. In most cases Section 'A' includes the PCM power and ground circuit tests, No MIL, No DLC Communication, No Start Tests and the Code Repair Tables. Section 'B' includes Driveability Symptoms. Section 'C' includes Component checks of various PCM systems (i.e., Emission Controls, Fuel, Speed Control and Ignition systems). Diagnosis of the OBD II system on GM vehicles starts with an OBD System Check.