Important: The following steps must be completed before using the symptom tables.
| • | There are no codes set. | 
| • | The navigation radio can communicate with the global positioning system (GPS) antenna. | 
| • | Inspect for aftermarket devices which could affect the operation of the navigation system. Refer to Checking Aftermarket Accessories in Wiring Systems. | 
| • | Inspect the system components for obvious damage or conditions which could cause the symptom. | 
Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom:
| • | Navigation radio buttons do not function properly. Refer to Navigation Diagnostic Self-Test Features . | 
| • | Navigation radio does not read the map disc. Refer to Diagnostic Trouble Code (DTC) List . | 
| • | The display is inoperative, discolored, or not clear. Refer to Navigation System Display Inoperative . |