For 1990-2009 cars

### Diagnostic Aids

The customer concern may have been due to a lack of cellular service in a given area or a failure in the National Cellular Network infrastructure that has since been corrected.

Step | Action | Yes | No
--- | --- | --- | ---
Schematic Reference: OnStar Schematics Connector End View Reference: Cellular Communication Connector End Views
1 | Did you perform the Cellular Communication Diagnostic System Check? | Go to Step 2 | Go to Diagnostic System Check - Cellular Communication
2 | Attempt to honk the horn, operate the lights and lock or unlock the doors on the vehicle. Does the applicable system operate properly? | Go to Step 3 | Go to

• | Diagnostic Starting Point - Horns in Horns

• | Diagnostic Starting Point - Lighting Systems in Lighting Systems

• | Diagnostic Starting Point - Doors in Doors

3 | Important: It is necessary to inform the OnStar® Call Center advisor that this call is for vehicle diagnostic purposes.

1. Contact the OnStar® Call Center by pressing the blue OnStar® button.
2. Ask the OnStar® advisor to perform a remote function (door lock/unlock, light flash, or horn honk).

Was the attempt successful?

Go to Diagnostic Aids

Use the scan tool to access the STID and ESN and contact the General Motors Technical Assistance Center