GM Service Manual Online
For 1990-2009 cars only

Diagnostic Instructions

    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Circuit/System Description

The communication interface module has the capability of commanding the horn, initiating door lock/unlock, or operating the exterior lamps using the serial data circuits. These functions are commanded by the Call Center per a customer request.

Diagnostic Aids

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

Reference Information

Schematic Reference

Telematics Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Telematics Description and Operation

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

Important: 

   • It is necessary to inform the Call Center advisor that this call is for vehicle diagnostic purposes.
   • It is necessary to have the vehicle in an open outside area where a cellular call can be successfully placed and GPS data can be received from satellites.

  1. Verify that the horn, lights, and the doors locks on the vehicle operate properly.
  2. If the applicable system does not operate properly, refer to Diagnostic System Check - Vehicle .
  3. Contact the Call Center by pressing the blue button. Verify with the call center advisor that all of the remote functions (door locks, lights, or horn) work.
  4. If unable to connect with the call center, refer to Unable to Contact Telematics Call Center .
    If the remote functions do not operate when requested, replace the communication interface module.

Repair Instructions

Perform the Diagnostic Repair Verification .

Control Module References for Communication Interface module replacement, setup, and programming