No Global Positioning System (GPS) Reception
No Global Positioning System (GPS) Reception
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 navigation antenna is connected to the telematics communication interface control module. The module supplies 5 V to the antenna to power the internal amplifier through the center conductor of the antenna coax cable.
When the vehicle is equipped with the optional navigation radio, a navigation signal splitter is installed to distribute the navigation signal to both the telematics communication interface control module and the navigation radio. The telematics communication interface control module supplies 5 V through the coax cable to power the internal antenna amplifier through the signal splitter.
Diagnostic Aids
* The telematics communication interface control module 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 initially 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.
* The GPS requires a clear line of sight to the sky to operate properly. In most cases the GPS will not have reception near tall buildings or inside structures.
Reference Information
Schematic Reference
* OnStar Schematics OnStar Schematics
* Radio/Navigation System Schematics Radio/Navigation System Schematics
Connector End View Reference
Component Connector End Views 1-2 Shift Solenoid (SS) Valve (M30)
Description and Operation
* OnStar Description and Operation OnStar
* Radio/Audio System Description and Operation Radio/Audio System
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 Control Module References for scan tool information
Special Tools
EL-49903 - GM OnStar Antenna Diagnostic Tool Kit
Circuit/System Verification
Note: The following verification requires the vehicle to be outside with an unobstructed view of the southern sky. Allow 5 minutes after turning the ignition ON for the GPS satellites to acquire vehicle signal.
1. Ignition ON.
2. Verify that no DTCs are set.
• If any DTCs are set
Refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle
• If no DTCs are set
3. Verify that an OnStar advisor can locate the vehicle after performing a blue button press.
• If the advisor can not locate the vehicle and the vehicle is not equipped with a navigation radio
Refer to Circuit System Testing Without Navigation Radio.
• If the advisor can not locate the vehicle and the vehicle is equipped with a navigation radio
Refer to Circuit System Testing With Navigation Radio.
• If the advisor can locate the vehicle
4. Verify that the NO GPS symbol/message is not displayed on the radio.
• If the NO GPS symbol/message is displayed
Refer to Circuit System Testing With Navigation Radio.
• If the NO GPS symbol/message is not displayed
5. All OK.
Circuit/System Testing (without Navigation Radio)
Note:
* The vehicle may be equipped with sectioned coax. Test each section and replace only the faulty section, not the entire length of coax.
* The following verification requires the vehicle to be outside with an unobstructed view of the southern sky. Allow 5 minutes after turning the ignition ON for the GPS satellites to acquire vehicle signal.
1. Ignition OFF, disconnect the GPS and cellular coax cable connector at the K73 telematics communication interface control module.
2. Using the EL-49903-3 kit (EL-49903-5 adapter and EL-49903-4 coax cable), connect theEL-49903 - GM OnStar antenna diagnostic tool kit to the K73 telematics communication interface module. Place the test antenna on the roof of the vehicle, ignition ON.
3. Verify that an OnStar advisor can locate the vehicle after performing a blue button press.
• If the advisor can not locate the vehicle
Replace the K73 telematics communication interface control module.
• If the advisor can locate the vehicle
4. Ignition OFF, disconnect the EL-49903 - GM OnStar antenna diagnostic tool kit from the K73 telematics communication interface control module
5. Disconnect the K73 telematics communication interface module coax at the T4G cellular phone, navigation, and digital radio antenna.
6. Test the coax cable between the K73 telematics communication interface control module and the T4G cellular phone, navigation, and digital radio antenna. Refer to component testing.
• If the coax cable does not pass the test
Replace the coax cable.
• If the coax cable passes the test
7. Test or replace the T4G cellular phone, navigation, and digital radio antenna.
Circuit/System Testing (with Navigation Radio)
Note:
* The vehicle may be equipped with sectioned coax. Test each section and replace only the faulty section, not the entire length of coax.
* The following verification requires the vehicle to be outside with an unobstructed view of the southern sky. Allow 5 minutes after turning the ignition ON for the GPS satellites to acquire vehicle signal.
1. Ignition OFF, disconnect the coax cable at the T15 navigation signal antenna splitter.
2. Using the EL-49903-3 kit (EL-49903-5 adapter and EL-49903-4 coax cable), connect the EL-49903 - GM OnStar antenna diagnostic tool kit to the navigation signal splitter. Place the test antenna on the roof of the vehicle, ignition ON.
3. Verify that the customer GPS concern is still present.
• If the GPS concern is not present
1. Ignition OFF, disconnect the EL-49903 - GM OnStar antenna diagnostic tool kit from the K73 telematics communication interface control module
2. Connect the GPS, T15 navigation antenna signal splitter, and cellular coax cable connector at the K73 telematics communication interface control module.
3. Disconnect the coax cable at the T4G cellular phone, navigation and digital radio antenna.
4. Test the coax cable between the T15 navigation antenna signal splitter and the T4G cellular phone, navigation and digital radio antenna. Refer to Component Testing.
• If the coax cable does not pass the test
Replace the coax cable.
• If the coax cable passes the test
5. Replace the T4G cellular phone, navigation and digital radio antenna.
• If the GPS concern is still present
4. Ignition OFF, disconnect the coax cable between the T15 navigation antenna signal splitter and the K73 telematics communication interface control module.
5. Using the EL-49903-3 kit (EL-49903-5 adapter and EL-49903-4 coax cable), connect the EL-49903 - GM OnStar antenna diagnostic tool kit to the telematics communication interface module. Place the test antenna on the roof of the vehicle, ignition ON
6. Verify that an OnStar advisor can locate the vehicle after performing a blue button press.
• If the advisor can not locate the vehicle
Replace the K73 telematics communication interface control module.
• If the advisor can locate the vehicle
7. Ignition OFF.
8. Test the coax cable between the navigation signal splitter and the K73 telematics communication interface control module. Refer to Component Testing.
• If the coax cable does not pass the test
Replace the coax cable.
• If the coax cable passes the test
9. Ignition OFF, disconnect the coax cable between the T15 navigation signal splitter and the A11 radio.
10. Connect the test antenna to the radio and place the test antenna on the roof of the vehicle.
11. Ignition ON.
12. Verify that the NO GPS symbol/message is not displayed on the radio.
• If the NO GPS symbol/message is displayed
Replace the A11 Radio
• If the NO GPS symbol/message is not displayed
13. Ignition OFF.
14. Test the coax cable between the T15 navigation antenna signal splitter and the A11 radio. Refer to Component Testing.
• If the coax cable does not pass the test
Replace the coax cable.
• If the coax cable passes the test
15. Replace the T15 navigation antenna 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 ohms between the coax cable center terminal end to end.
• If 5 ohms or greater
Replace the coax cable.
• If less than 5 ohms
3. Test for greater than 5 ohms between the coax cable outer shield end to end.
• If 5 ohms or greater
Replace the coax cable.
• If less than 5 ohms
4. Test for infinite resistance between the coax cable center terminal and the coax cable outer shield.
• If less than infinite resistance
Replace the coax cable.
• If infinite resistance
5. All OK.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the repair.
* Radio Antenna Base Replacement Radio Antenna Base Replacement
* Control Module References Control Module References for telematics communication interface control module replacement, programming and setup.