• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
• Review Strategy Based Diagnosis for an overview of the diagnostic approach.
• Diagnostic Procedure Instructions provides an overview of each diagnostic category.

The navigation antenna is connected to the navigation radio by a shielded coaxial cable. The radio supplies 5 V through the coax cable to power the internal antenna amplifier.

• Radio On.
• System voltage is greater than 9 V and less than 16 V.
• The navigation radio tests the GPS antenna every 10 seconds.

The navigation radio detects a short to B+ on the GPS antenna signal circuit.

The navigation radio detects a short to ground on the GPS antenna signal circuit.

The navigation radio detects an open/high resistance on the GPS antenna signal circuit.

• The radio uses the last reported position and the vehicle speed signal to calculate the vehicle position.
• Route guidance may be inaccurate.
• Turn by turn navigation may be inaccurate or inoperative.

• The condition responsible for setting the DTC no longer exists.
• A history DTC will clear once 50 consecutive malfunction-free ignition cycles have occurred.

The navigation antenna requires a clear line of sight to the sky to operate properly. The GPS may have limited, intermittent, or no reception near tall buildings or inside structures.

Radio/Navigation System Schematics

Master Electrical Component List

Radio/Audio System Description and Operation

• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs

Control Module References for scan tool information

EL-49903 GM OnStar Antenna Diagnostic Tool Kit

1. Ignition OFF/vehicle OFF, disconnect the navigation antenna coax cable connector at the A11 Radio. Connect the EL-49903 GM OnStar antenna diagnostic tool kit to the A11 Radio, place the test antenna on the roof of the vehicle.
2. Ignition ON/vehicle in Service Mode, radio ON, navigation selected.
3. Verify DTC B2462 is not set.
• If DTC B2462 is set

  Replace the A11 Radio.

• If DTC B2462 is not set
4. Ignition OFF/vehicle OFF, disconnect the radio navigation coax cable at the T2RR Antenna – Roof Rear.
5. 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
6. Test or replace the T2RR Antenna – Roof Rear.

1. Ignition OFF, disconnect the coax cable at both components.
2. Locate the appropriate pinout adaptor and load test loop adaptor from EL-52552 COAX FAKRA Cable Adaptor Kit.
3. Connect the 2 adaptors together, measure and record the resistance between the terminals at the pinout adaptor.
4. Disconnect the 2 adaptors and connect each one to the appropriate end of the coax cable.
5. At the pinout adapter, measure the total resistance of the coax cable loop including the connected load test adaptor.
• If not within 5 Ω of the reading from step 3.

  Replace the coax cable

• If within 5 Ω of the reading from step 3.
6. All OK.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• High Frequency Antenna Replacement
• Control Module References for radio replacement, programming, and setup.