Begin the system diagnosis with Diagnostic System Check - Vehicle. This procedure provides the following information:
| • | The identification of the control modules which command the system | 
| • | The ability of the control modules to communicate through the serial data circuit | 
| • | The identification of any stored diagnostic trouble codes (DTCs) and the codes' statuses | 
The Diagnostic System Check identifies the correct procedure for diagnosing the system and indicates where that procedure is located.