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HOMESERVICE MANUALSCHEVROLET2003TRAILBLAZER 4.2 S, 4WDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 1604 (CELLULAR COMMUNICATION SYSTEM)DIAGNOSTIC INFORMATION AND PROCEDURESGLOBAL POSITIONING SYSTEM (GPS) DATA NOT CURRENT OR INACCURATEDIAGNOSTIC AIDS
2003 Chevrolet TrailBlazer 4.2 S, 4WD

Diagnostic Aids

2003 Chevrolet TrailBlazer 4.2 S, 4WDSECTION Diagnostic Aids
WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2002 GMC Yukon XL, 2002 GMC Yukon, 2002 Chevrolet Tahoe, 2002 Chevrolet Suburban, and 2002 Cadillac Escalade EXT. However, it is still accessible from the selected car via links, so may be relevant.
  • 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 Interface Unit. Upon entering this screen, the "GPS Signal" title will automatically display "Yes", regardless of the presence of time increment, for at least two 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 made by a customer 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.
Global Positioning System (GPS) Data Not Current or Inaccurate

Step Action Values Yes No
Schematic Reference:  OnStar Schematics  
Connector End View Reference: Cellular Communication Connector End Views 
1 Did you perform the Cellular Communication Diagnostic System Check? - Go to Step 2  Go to Diagnostic System Check - Cellular Communication 
2
IMPORTANT: It is important to have the vehicle in an open outside area where a cellular call can be successfully placed and global positioning system (GPS) data can be received from satellites. It is also necessary to inform the OnStar® Call Center advisor that this call is for vehicle diagnostic purposes.
With a scan tool, observe the GPS signal status indicator in the GPS Data Display menu, for at least 10 seconds.Does the indicator display "Yes"?		 - Go to Step 3  Go to Step 6 
3
  1. Press the OnStar® Call Center button.
  2. Ask the OnStar® Call Center advisor if they have received GPS data.
Has the advisor received GPS data?		 - Go to Step 4  Go to Step 5 
4 Ask the OnStar® Call Center advisor to verify your position.
Is the location provided by the OnStar® Call Center advisor within a reasonable distance from the actual location of the vehicle?		 - Go to Diagnostic Aids Go to Step 10 
5 Ask the OnStar® Call Center advisor if this call was a fail to voice.
Was the call a fail to voice?		 - Contact the General Motors Technical Assistance Center Go to Step 6 
6
  1. Disconnect the navigation antenna coax from the navigation antenna within the wiring harness.
  2. Disconnect the navigation antenna from the vehicle interface unit (VIU).
  3. Measure the resistance from the center conductor of the coax to the metal outer shield.
Does the meter read out of limits?		 - Go to Step 7  Go to Step 8 
7 Measure the resistance of the navigation antenna coax center conductor from end to end.
Does the resistance measure greater than the specified value?		 1.0 Ω Go to Step 8  Go to Step 9 
8 Replace the navigation antenna coax.
Did you complete the replacement?		 - Go to Step 11  -
9 Replace the navigation antenna assembly. Refer to Navigation Antenna Replacement .
Did you complete the replacement?		 - Go to Step 11  -
10 Replace the Vehicle Interface Unit. Refer to OnStar Vehicle Interface Unit (VIU) Replacement .
Did you complete the replacement?		 - Go to Step 11  -
110 Operate the system in order to verify the repair.
Did you correct the condition?		 - Go to Step 2  System OK
RENDER: 1.0x

NO RELATED

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Stop DIY work and contact a certified mechanic immediately if any of the following apply:

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  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.