The number(s) below refer to the step number(s) on the diagnostic table.
It is necessary for the OnStar® Call Center to command ON and OFF the horn.
Tests that the problem is not within any other system.
Step  | Action  | Yes  | No  | 
|---|---|---|---|
Schematic Reference: OnStar Schematics  | |||
1  | Did you perform the OnStar® Diagnostic System Check?  | Go to Step 2  | |
 Do the Headlamps turn ON and OFF with each command?  | Go to Step 6  | Go to Step 3  | |
 Do the Headlamps turn ON and OFF with each command?  | Go to Step 4  | ||
4  | Inspect for poor connections at the VIU. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?  | Go to Step 6  | Go to Step 5  | 
5  | Replace the VIU. Refer to OnStar Vehicle Interface Unit Replacement Did you complete the replacement?  | Go to Step 6  | --  | 
6  | Operate the system in order to verify the repair. Did you correct the condition?  | System OK  | Go to Step 2  |