Begin the system diagnosis with the Diagnostic System Check - Retained Accessory Power . The Diagnostic System Check will provide the following information:
| • | The identification of the control module which commands the system | 
| • | The ability of the control module to communicate through the serial data circuit | 
| • | The identification of any stored DTCs and their status | 
The use of the Diagnostic System Check will identify the correct procedure for diagnosing the system and where the procedure is located.