A Symptoms

IMPORTANT: The following steps must be completed before using the symptom tables.

1. Perform the Diagnostic System Check Cellular Communication before using the Symptom Tables in order to verify that all of the following are true:
^ There are no DTCs set.
^ The control modules can communicate via the serial data link. Diagnostic System Check
2. Review the system operation in order to familiarize yourself with the system functions. Refer to Cellular Telephone Description and Operation.

Visual/Physical Inspection
^ Inspect for aftermarket devices which could affect the operation of the system. Refer to Checking Aftermarket Accessories in Diagrams.
^ 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 and Poor Connections in Diagrams.

Symptom List
Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom:
^ Cellular Telephone Inoperative
^ Cellular Telephone - Hands Free Operation Inoperative
^ Cellular Telephone - Voice Inoperative During Hands-Free (W/O U45) or Cellular Telephone - Voice Inoperative During Hands-Free (W/U45)
^ Cellular Telephone - Audio Inoperative During Hands-Free
^ Cellular Telephone - Noisy Audio During Hands-Free
^ Radio Does Not Connect to Internet Service Provider (U45)
^ OnStar One or More Buttons Inoperative
^ Unable to Contact OnStar Call Center
^ Microphone Inoperative - Caller Cannot Be Heard
^ OnStar Button LED Inoperative
^ No (or Noisy) OnStar Audio

"For a description of the RPO Code(s) shown in this article or any of the images therein, refer to the RPO Code List found at Vehicle/Application ID". RPO Codes