GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2007 🢒 CTS 🢒 Diagnostic Navigation 🢒 Vehicle Diagnostic Information 🢒 OnStar Global Positioning System (GPS) Data Not Current or Inaccurate

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 navigation antenna is connected to the vehicle communication interface module (VCIM) with a RG-174 coax cable. The VCIM polls the data from the navigation antenna once every second.

Diagnostic Aids
    • The GPS signal title on the scan tool will display a Yes or No dependant upon whether or not the module sees an increment of the seconds transmitted by GPS signals to the vehicle communication interface module. Upon entering this screen, the GPS signal title will automatically display Yes, regardless of the presence of time increment, for at least 2 seconds, while the algorithm in the scan tool determines the status of the clock. If increment is found, Yes is continually displayed. If the clock remains static, No is displayed. The scan tool looks for increment every second, regardless of current display.
    • Inaccurate or aged GPS position concerns which are no longer present may have been due to the temporary loss of GPS signal reception by the vehicle. Conditions such as driving through tunnels or parking structures while making an OnStar® keypress will restrict the navigation antenna from a clear view of the satellites in the sky and may have caused this temporary data loss.

Reference Information

Schematic Reference

OnStar Schematics

Connector End View Reference

Entertainment/Communication Connector End Views

Electrical Information Reference

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

Scan Tool Reference

    •  Scan Tool Data List
    •  Scan Tool Data Definitions

Circuit/System Verification
  1. With the scan tool, observe the GPS signal status indicator for at least 10 seconds. Verify the indicator displays Yes.
    2. ⇒If the indicator does not display Yes, go to Component Testing.
  2. Call and verify the OnStar advisor receive GPS data.
    3. ⇒If the advisor did not receive GPS data and the call was a 'fail to voice', contact the GM Technical Assistance Center.
    ⇒If the advisor did not received GPS data and the call was not a 'fail to voice' , go to Component Testing.
  3. Verify with the OnStar Call Center advisor that your actual position is within a reasonable distance from the actual location of the vehicle.
    4. ⇒If your actual position is not within a reasonable distance from the actual location of the vehicle, replace the VCIM.

Component Testing

Important: Vehicle may be equipped with sectioned coax. Test each section and replace only the faulty section, not the entire length or coax.

  1. Disconnect the navigation antenna coax cable from the navigation antenna within the wiring harness.
  2. Disconnect the navigation antenna from the VCIM.
  3. Test for infinite resistance between the center conductor of the coax to the metal outer shield.
    4. ⇒If it does not read infinite, replace the navigation antenna coax cable.
  4. Test for greater than 1 ohm resistance at the navigation antenna coax center conductor from end to end.
    5. ⇒If less than specified value, replace the navigation antenna assembly.
    ⇒If greater specified value, replace the navigation antenna coax cable.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Cellular Communications/Digital Radio Antenna Replacement
    •  Control Module References for VCIM replacement, setup, and programming