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 prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* 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(R) keypress will restrict the navigation antenna from a clear view of the satellites in the sky and may have caused this temporary data loss.

Circuit/System Verification

1. Observe the scan tool GPS Signal Status Indicator parameter for at least 10 seconds. Verify the indicator displays Yes.

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

2. Call and verify the OnStar advisor receive GPS data.

• 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 receive 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 VCIM.

Circuit/System 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. Ignition OFF, disconnect the navigation antenna coax from the VCIM module and the navigation antenna.
2. Ignition ON, test for less than 1 volt between the antenna coax center terminal and ground.

• If greater than the specified range, replace the antenna coax.

3. Test for infinite resistance between the antenna coax center terminal and ground.

• If less than the specified value, replace the antenna coax

4. Test for less than 5 ohms of resistance at the antenna coax connector outer shield from end to end.

• If greater than specified value, replace the antenna coax cable.

5. Test for less than 5 ohms of resistance at the antenna coax center conductor from end to end.

• If greater than specified value, replace the antenna coax cable.

6. Test for infinite resistance between the antenna coax center terminal and the outer shield.
7. If coax cable tests normal, test or replace the navigation antenna.

Repair Instructions

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

* Cellular Communications/Digital Radio Antenna Replacement