Important: The following steps must be completed before using the symptom tables.
- Perform   
Diagnostic System Check - Lighting Systems 
       before using the Symptom Tables in order
to        verify that all of the following are  true:
 
| •  | The control module(s) can communicate via the serial data link. | 
 
- Review the system operation and circuit descriptions that apply
      to the customer complaint in order to familiarize yourself with the
    system          functions. Refer to the following list:
 
Visual/Physical Inspection
|     •  | Inspect the easily accessible or visible system components for
      obvious damage or conditions which could cause the symptom. | 
 
Intermittent
Faulty electrical connections or wiring may be the cause of intermittent
      conditions. Refer to    
Testing for Intermittent Conditions and Poor Connections 
       in Wiring  Systems.
Symptom List
Refer to a symptom diagnostic procedure from the following list in order
      to diagnose the symptom: