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 cellular phone and navigation antenna is connected to the telematics communication interface control module. This module supplies 5 V to the cellular phone and navigation antenna to power the internal amplifier. A navigation signal splitter is installed to distribute the GPS signal to both the telematics communication interface control module and the navigation radio. The navigation radio supplies 5 V through the GPS antenna coaxial cable to the navigation signal splitter to power the internal navigation radio signal amplifier.

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 telematics communication interface control 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

OnStar Malfunction without Navigation Radio
1. Ignition OFF, disconnect the GPS and cell coax cable connector at the K73 telematics communication interface control module.
2. Using the EL-49903-5 adapter with EL-49903-4 coax cable, connect the EL-49903 to the K73 telematics communication interface control module.
3. Ignition ON, wait 5 minutes, then contact the OnStar call center consultant by pressing the blue OnStar button. A call center consultant should answer the call, ask the consultant to verify the vehicle location to confirm the GPS system is functioning.

• If the OnStar GPS does not function, replace the K73 telematics communication interface module.

4. Ignition OFF, perform the coax cable test on the coax cable, refer to Component Testing. The coax cable should pass the test.

• If the coax cable does not pass the test, replace the coax cable.

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

OnStar Malfunction with Navigation Radio
1. Ignition OFF, disconnect the GPS and cell coax cable connector at the K73 telematics communication interface module.
2. Using the EL-49903-5 adapter with EL-49903-4 coax cable, connect the EL-49903 to the K73 telematics communication interface control module.
3. Ignition ON, wait 5 minutes, then contact the OnStar call center consultant by pressing the blue OnStar button. A call center consultant should answer the call, ask the consultant to verify the vehicle location to confirm the GPS system is functioning.

• If the OnStar GPS does not function, replace the K73 telematics communication interface module.

4. Ignition OFF, reconnect the coax cable to the K73 telematics communication interface module. Disconnect the coax cable from the T15 navigation signal splitter.
5. Ignition ON, 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.

6. Ignition OFF, reconnect the coax cable to the T15 navigation signal splitter. Disconnect the coax cable from the T4G cellular phone, navigation and digital radio antenna.
7. Ignition ON, test for 4.5-5.5 V between the coax cable center conductor and the outer shield.

• If within the specified range, replace the T4G cellular phone, navigation and digital radio antenna.

8. Ignition OFF, perform the coax cable test on the coax cable between the T15 navigation signal splitter and the T4G cellular phone, navigation and digital radio antenna, refer to Component Testing. The coax cable should pass the test.

• If the coax cable does not pass the test, replace the coax cable.
• If the coax cable passes the test, replace the T15 navigation and signal splitter.

Component Testing

Caution: Refer to Test Probe Caution (Test Probe Caution).

Note: Before testing the coax cable, check the cable exterior for being pinched, cut, damaged, or having loose connections at the components, which can cause reception issues.

To prevent false reading when testing the center coax terminals, use care not to ground the test probe on the outer housing/shield.

Coax Cable Test
1. Ignition OFF, disconnect the coax cable at both components.
2. Test for less than 5 ohm between both ends of the coax cables center terminals.

• If greater than the specified range, replace the failed coax cable.

3. Test for greater than 10k ohm between the coax cable center wire and the outer coax shield.

• If less than the specified range, replace the coax cable.

Repair Instructions

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

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