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Symptoms-Cellular Communication: Notes

WARNING: This page is about a different car, the 2003 GMC Sierra, 2003 GMC Cab & Chassis Sierra, 2003 Chevrolet Silverado, and 2003 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
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 not 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   . 
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