B125D

DTC B125C or B125D

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.



DTC Descriptors
DTC B125C 01
- Satellite Antenna 1 Circuit Short to Battery

DTC B125C 02
- Satellite Antenna 1 Circuit Short to Ground

DTC B125C 04
- Satellite Antenna 1 Circuit Open Circuit




Circuit/System Description

The digital radio receiver (DRR), located inside the radio, receives digital radio information from a specific digital radio antenna located on the outside of the vehicle. The DRR is connected to the digital radio antenna via a shielded antenna coax cable.


Conditions for Running the DTC

This test is run every 300 milliseconds.


Conditions for Setting the DTC

The radio detects an antenna fault.


Action Taken When the DTC Sets

The radio displays "No XM Signal" or "Check Antenna".


Conditions for Clearing the DTC

* The condition for setting the DTC is no longer present.
* The DTC clears after 100 malfunction-free ignition cycles.



Reference Information
Schematic Reference

Radio/Navigation System Schematics (Radio/Navigation System Schematics)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Radio/Audio System Description and Operation (Radio/Audio System Description and Operation)
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Special Tools

EL-48028 Digital Radio Test Antenna


Circuit/System Verification

1. Contact XM at 1-800-852-9696 to verify customer account status or possible network problems.
2. Ensure the vehicle is outside in an area with an unobstructed view of the southern sky. Turn ON XM radio. Tune the radio to satellite channel 1. Reception should be clear.



Circuit/System Testing


Important: Check for the proper operation of the OnStar(R) System prior to performing this diagnostic. Address any concerns with the OnStar(R) System prior to diagnosing or repairing the XM radio concern.


1. Ignition OFF, disconnect the DRR antenna coax from the radio. Connect the EL-48028 to the radio and place on the roof of the vehicle.
2. Ignition ON, radio tuned to XM. Verify XM reception has improved.

• If the reception is not improved, replace the radio.

3. Ignition OFF, disconnect the antenna coaxial from the digital radio antenna.
4. Test for less than 5 ohms end to end at the coax center conductor.

• If greater than the specified range, replace the antenna coax.

5. Test for less than 5 ohms end to end at the coax outer shield.

• If greater than the specified range, replace the antenna coax.

6. Test for infinite resistance between the antenna coax center conductor and the outer shield.

• If less than the specified range, replace the antenna coax.

7. If all circuits test normal, replace the digital radio antenna.



Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.


Control Module References (Programming and Relearning)for DRR replacement, setup, and programming