No Global Positioning System (GPS) Reception
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No Global Positioning System (GPS) Reception
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Circuit/System Description
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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 thorough 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.
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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.
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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.
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The global positioning system (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.
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Schematic Reference
Connector End View Reference
Component Connector End Views
Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References
for scan tool information
Special Tools
EL-49903 GM OnStar Antenna Diagnostic Tool Kit
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Circuit/System Verification
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Note
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The following verification requires the vehicle to be outside with an unobstructed view of the southern sky. Allow 5 minutes after turning key on for the GPS satellites to acquire vehicle signal.
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1.
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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, verifying the vehicle OnStar system is functioning and the consultant can locate the vehicle.
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2.
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If the OnStar system is not functioning and the vehicle is not equipped with a navigation radio, refer to Circuit System Testing Without Navigation Radio.
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3.
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If the OnStar system is not functioning and the vehicle is equipped with a navigation radio, refer to Circuit System Testing With Navigation Radio.
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4.
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If equipped, verify the Navigation Radio functions while driving the vehicle.
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5.
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If the navigation radio does not function, refer to Circuit System Testing With Navigation Radio.
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Without Navigation Radio
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1.
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Ignition OFF, disconnect the coax cable connector at the K73 telematics communication interface control module.
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2.
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Using the EL-49903-3 kit (EL-49903-5 adapter and EL-49903-4 coax cable), connect the EL-49903 to the K73 telematics communication interface module, place the test antenna on the roof of the vehicle.
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3.
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Ignition ON, verify DTC B2462 is not set in the K73 telematics communication interface module.
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4.
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If DTC B2462 is set as current, replace the K73 telematics communication interface module.
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5.
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Ignition OFF, disconnect the K73 telematics communication interface module coax at the T4G cellular phone, navigation, and digital radio antenna.
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6.
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Perform the coax cable test on the coax cable, refer to Component Testing. The coax cable should pass the test.
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7.
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If the coax cable does not pass the test, replace the coax cable.
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8.
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If all circuits test normal, replace the T4G cellular phone, navigation, and digital radio antenna.
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With Navigation Radio
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1.
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Ignition OFF, disconnect the coax cable connector at the K73 telematics communication interface control module.
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2.
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Using the EL-49903-3 kit (EL-49903-5 adapter and EL-49903-4 coax cable), connect the EL-49903 to the K73 telematics communication interface module, place the test antenna on the roof of the vehicle.
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3.
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Ignition ON, verify DTC B2462 is not set in the K73 telematics communication interface module.
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4.
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If DTC B2462 is set as current, replace the K73 telematics communication interface module.
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5.
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Ignition OFF, disconnect the navigation antenna coax cable connector at the A11 radio.
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6.
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Connect the EL-49903 to the A11 radio, place the test antenna on the roof of the vehicle.
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7.
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Ignition ON, verify DTC B2462 is not set in the A11 radio.
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8.
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If DTC B2462 is set as current, replace the A11 radio.
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9.
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Ignition OFF, reconnect the antenna coax cable connections at both the K73 telematics communication interface module and the A11 radio.
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10.
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Disconnect the K73 telematics communication interface module coax at the T15 navigation signal splitter.
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11.
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Ignition ON, test for 4.5-5.5 V between the coax cable center conductor and the outer shield.
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12.
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If not within the specified range, replace the coax cable.
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13.
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Ignition OFF, disconnect the A11 radio navigation coax at the T15 navigation signal splitter.
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14.
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Ignition ON, test for 4.5-5.5 V between the coax cable center conductor and the outer shield.
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15.
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If not within the specified range, replace the coax cable.
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16.
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Disconnect the antenna coax cable from the T15 navigation signal splitter and the T4G cellular phone, navigation and digital radio antenna.
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17.
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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.
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18.
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If the coax cable does not pass the test, replace the coax cable.
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19.
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Reconnect all coax cable connections at the T15 navigation signal splitter.
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20.
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Ignition ON, test for 4.5-5.5 V between the coax cable center conductor and the outer shield at the T4G cellular phone, navigation and digital radio antenna .
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21.
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If not within the specified range, replace the T15 navigation signal splitter.
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22.
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If all circuits test normal, replace the T4G cellular phone, navigation and digital radio antenna.
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Refer to
Test Probe Caution
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Note
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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.
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To prevent false reading when testing the center coax terminals, use care not to ground the test probe on the outer housing/shield.
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Coax Cable Test
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1.
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Ignition OFF, disconnect the coax cable at both components.
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2.
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Test for less than 5 Ω between both ends of the coax cables center terminals.
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3.
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If greater than the specified range, replace the coax cable
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4.
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Test for less than 5 Ω between both ends of the coax cable outer shield.
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5.
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If greater than the specified range, replace the coax cable
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6.
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Test for infinite resistance between the coax cable center wire and the outer coax shield.
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7.
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If less than the specified range, replace the coax cable.
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Perform the
Diagnostic Repair Verification
after completing the diagnostic procedure.
