Buick Regal: Digital Radio Poor or No Reception

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.
• Refer to Diagnostic Procedure Instructions for an overview of each diagnostic category.

DTC Descriptors

DTC B125C 01

Satellite Antenna Circuit Short to Battery

DTC B125C 02

Satellite Antenna Circuit Short to Ground

DTC B125C 04

Satellite Antenna Circuit Open

Circuit/System Description

The digital radio receiver, located inside the radio, receives digital radio information from the digital radio antenna located on the outside of the vehicle. The digital radio receiver is connected to the digital radio antenna via a shielded coax cable. The digital radio antenna contains an amplifier which is powered by the radio through the coax cable.

Conditions for Running the DTC

This DTC is run every 300 milliseconds.

Conditions for Setting the DTC

The radio detects a circuit fault in the digital radio antenna.

Action Taken When the DTC Sets

The radio displays No XM Signal or Check Antenna.

Conditions for Clearing the DTC

• A current DTC clears when the condition for setting the DTC is no longer present.
• A history DTC clears after 100 malfunction-free ignition cycles.

Diagnostic Aids

The digital radio antenna requires a clear line of sight to the sky to operate properly. Reception may be limited, intermittent, or unavailable inside structures.

Reference Information

Schematic Reference

Radio/Navigation System Wiring Schematics (IOB) , Radio/Navigation System Wiring Schematics (IOR) or Radio/Navigation System Wiring Schematics (IO5/IO6) , or Radio/Navigation System Wiring Schematics (IOS/IOT).

Connector End View Reference

Component Connector End View Index

Description and Operation

Radio/Audio System Description and Operation (IO6) , Radio/Audio System Description and Operation (IOB) , or Radio/Audio System Description and Operation (IOS/IOT/IOU).

Electrical Information Reference

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

Special Tools

EL-48028 Digital Radio Test Antenna

Circuit/System Verification

1. With the vehicle outside in an area with an unobstructed view of the southern sky, tune to XM.

2. Verify DTC B125C is not set as current and the No XM Signal message is not displayed on the radio.

• If DTC B125C is set as current or the No XM Signal message is displayed.

Refer to Circuit/System Testing.

• Go to next step: If DTC B125C is not set as current and the No XM Signal message is not displayed.

3. All OK.

Circuit/System Testing

1. Ignition OFF/Vehicle OFF, disconnect the digital radio antenna coax cable from the A11 Radio.

Connect the EL-48028 Digital Radio Test Antenna to the radio and place on the roof of the vehicle.

2. Ignition ON/Vehicle in Service Mode, radio tuned to XM channel 1.

3. Verify DTC B125C is not set as current and XM reception is improved.

• If DTC B125C is set as current or XM reception is not improved

Replace the A11 Radio.

• Go to next step: If DTC B125C is not set as current and XM reception is improved

4. Ignition OFF/Vehicle OFF, disconnect the digital radio antenna coax cable from the T2RR Antenna - Roof Rear.

5. Verify the digital radio antenna coax cable passes the coax cable component test. Refer to Component Testing.

• If the coax cable does not pass the test

Replace the antenna coax cable

• Go to next step: If the coax cable passes the test

6. Test or replace the T2RR Antenna - Roof Rear.

Component Testing

CAUTION: Refer to Test Probe Caution.

NOTE: Before testing the coax cable, check the cable exterior for being pinched, cut, damaged, or having loose connections at the components, which can cause reception issues.

To prevent false reading when testing the center coax terminals, use care not to ground the test probe on the outer housing/shield.

Coax Cable Test

1. Ignition OFF/Vehicle OFF, disconnect the coax cable at both components.

2. Test for less than 5 Ω between coax cable center terminal end to end.

• If 5 Ω or greater

Replace the coax cable

• Go to next step: If less than 5 Ω

3. Test for less than 5 Ω between the coax cable outer shield end to end.

• If 5 Ω or greater

Replace the coax cable

• Go to next step: If less than 5 Ω

4. Test for infinite resistance between the coax cable center terminal and the coax cable outer shield.

• If less than infinite resistance

Replace the coax cable

• Go to next step: If infinite resistance

5. All OK

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

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

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