Circuit/System Testing

Ignition 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, infotainment system ON, navigation selected.
Verify DTC B2462 is not set.
- If DTC B2462 is set
  Replace the K74 Human Machine Interface Control Module.
- If DTC B2462 is not set
Ignition OFF, disconnect the radio navigation coax cable at the T4P Navigation 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
- If the coax cable passes the test
Test or replace the T4P Navigation Antenna.