Circuit/System Testing

Ignition OFF/vehicle OFF, disconnect the navigation antenna coax cable connector at the K74 Human Machine Interface Control Module. Connect the EL-49903 GM OnStar antenna diagnostic tool kit to the K74 Human Machine Interface Control Module, place the test antenna on the roof of the vehicle.
Ignition ON/vehicle in Service Mode, infotainment system ON, navigation selected.
Verify DTC B2462 is not set or the NO GPS symbol is not displayed on the information display.
- If DTC B2462 is set or the NO GPS symbol is displayed
  Replace the K74 Human Machine Interface Control Module.
- Go to next step: If DTC B2462 is not set or the NO GPS symbol is not displayed
Ignition OFF/vehicle OFF, disconnect the radio navigation coax cable at the T4G Cellular Phone, Navigation, and Digital Radio Antenna.
Verify the radio navigation coax cable passes the coax cable component test. Refer to Component Testing.
- If the coax cable does not pass the test
  Replace the coax cable
- Go to next step: If the coax cable passes the test
Test or replace the T4G Cellular Phone, Navigation, and Digital Radio Antenna.