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Symptoms - Cellular Communication: Notes

IMPORTANT: The following steps must be completed before using the symptom tables.
  1. Perform the Diagnostic System Check - Vehicle (without HP2) or Diagnostic System Check - Vehicle (with HP2) . Before using the Symptom Tables, verify that all of the following are true:
    • There are no DTCs set.
    • The control module can communicate via the serial data link.
  2. Review the system operation in order to familiarize yourself with the system functions. Refer to OnStar Description and Operation .
  3. Perform the OnStar Symptom Diagnosis . This symptom table will enable the user to verify the customer complaint and narrow it to its source.
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