OnStar Global Positioning System (GPS) Data Not Current or Inaccurate

OnStar Global Positioning System (GPS) Data Not Current or Inaccurate

Diagnostic Instructions

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

Circuit/System Description

The telematics communication interface control module receives information from a specific cellular phone and navigation antenna located on the outside of the vehicle. The cellular phone and navigation antenna is connected to the telematics communication interface control module via a shielded coaxial cable. The antenna cable also provides a path for DC current for powering the antenna.

Diagnostic Aids

* The GPS signal title on the scan tool will display a Yes or No dependent 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 tunnels or parking structures will restrict the cellular phone and 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 (OnStar Schematics)
Connector End View Reference

Component Connector End Views (Connector End Views By Name)
Description and Operation

OnStar Description and Operation (OnStar)
Electrical Information Reference

* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)

Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information

Circuit/System Verification

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

1. Ignition ON, observe the GPS signal status indicator for at least 10 seconds with a scan tool. The indicator should display Yes.

• If the indicator does not display Yes, refer to Circuit/System Testing.

2. Call and verify the OnStar advisor has received the GPS data.

• If the advisor did not receive the GPS data and the call was a 'fail to voice', contact the GM Technical Assistance Center.
• If the advisor did not receive the GPS data and the call was not a 'fail to voice', refer to Circuit/System 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.

• If your actual position is not within a reasonable distance from the actual location of the vehicle, replace the K73 telematics communication interface control module.

Circuit/System Testing

1. Disconnect the cellular phone and navigation antenna coax cable from the K73 telematics communication interface control module.
2. Ignition ON, test for 4.5-5.5 V between the K73 telematics communication interface control module coax cable center conductor terminal at the module and ground.

• If not within the specified range, replace the K73 telematics communication interface control module.

3. Reconnect the coax cable to the telematics communication interface control module. Disconnect the coax cable from the T4G cellular phone and navigation antenna.
4. Test for 4.5-5.5 V between the coax cable center conductor and the outer shield.

• If not within the specified range, replace the coax cable.

5. If all circuits test normal, replace the T4G cellular phone and navigation antenna.

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Radio Antenna Base Replacement (Radio Antenna Base Replacement)
* Control Module References (Programming and Relearning) for telematics communication interface control module replacement, setup, and programming