For 1990-2009 cars

### Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

1. It is necessary for the OnStar® Call Center to command ON and OFF the horn.

2. 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 | Go to OnStar System Check
2 |

1. Activate the OnStar® Call Button.
2. Wait for the Call Center operator to answer.
3. Ask the operator for a Lock command.

Does the Lock turn ON and OFF with each command?

Go to Step 6

Go to Step 3

3 |

1. Install a scan tool.
2. Turn ON the ignition, with the engine OFF.
3. With a scan tool, command the Lock ON and OFF.

Does the Lock turn ON and OFF with each command?

Go to Step 4

Go to Diagnostic System Check - Door Systems

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