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Tahoe / Yukon Service Manual

DTC B1784

Cellular, Entertainment, and Navigation | Diagnostic Information and Procedures | Document ID: 5191886 Diagnostic Instructions 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. DTC Descriptors DTC B1784 Global Positioning System Antenna Coaxial Signal For Symptom Byte information refer to: Symptom Byte List Diagnostic Fault Information

Circuit Short to Ground Open/High Resistance Short to Voltage Signal Performanc
Coax Cable B1784 11 B1784 13 B1784 12 —

Circuit/System Description The A11 Radio receives information from the GPS antenna element which is part of the T4P High Frequency Antenna located on the outside of the vehicle. The GPS antenna element is connected to the A11 Radio via a shielded coaxial cable. The A11 Radio supplies 5 V through the coax cable to power the internal antenna amplifier. Conditions for Running the DTC Ignition ON. System voltage is between 9-16 V. Conditions for Setting the DTC B1784 11 Short to ground on the GPS antenna signal circuit. B1784 12 Short to voltage on the GPS antenna signal circuit. B1784 13 Open/high resistance on the GPS antenna signal circuit. Action Taken When the DTC Sets The A11 Radio will not receive vehicle location. The navigation system will be inoperative/inaccurate. Conditions for Clearing the DTC The A11 Radio detects the presence of a GPS antenna. A history DTC will clear once 100 consecutive malfunction-free ignition cycles have occurred. Reference Information Schematic Reference Radio/Navigation System Schematics Connector End View Reference Master Electrical Component List Description and Operation Radio/Audio System Description and Operation Electrical Information Reference Circuit Testing Connector Repairs Testing for Intermittent Conditions and Poor Connections Wiring Repairs Scan Tool Reference Control Module References for scan tool information Special Tools EL-49903 GM OnStar Antenna Diagnostic Tool Kit Circuit/System Testing

  1. Ignition OFF, disconnect the GPS coax cable connector at the A11 Radio.
  2. Connect the EL-49903-1 OnStar Test Antenna, Navn-Cell Comn to the A11 Radio. Place the test antenna on the roof of the vehicle, ignition ON/vehicle in Service Mode.
  3. Verify DTC B1784 is not set or the vehicle location from the GPS is correct. ⇒ If DTC B1784 is set or the vehicle location from the GPS is not correct Replace the A11 Radio. ⇓ If DTC B1784 is not set or the vehicle location from the GPS is correct
  4. Ignition OFF, disconnect the EL-49903-1 OnStar Test Antenna, Navn-Cell Comn from the A11 Radio.
  5. Disconnect the GPS coax cable at the T4P High Frequency Antenna.
  6. Test the coax cable between the A11 Radio and the T4P High Frequency 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 T4P High Frequency Antenna. Component Testing
  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. Repair Instructions Perform the Diagnostic Repair Verification after completing the diagnostic procedure. High Frequency Antenna Replacement Control Module References Control Module replacement, programming and setup.