Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSGMC2019SIERRA 1500 LIMITED BASE, 4WD, GASREPAIR AND DIAGNOSIS (SINGLE PAGE)ACCESSORIES & EQUIPMENTENTERTAINMENT SYSTEMSCELLULAR, ENTERTAINMENT, AND NAVIGATION - DIAGNOSTIC INFORMATION AND PROCEDURESDIAGNOSTIC INFORMATION AND PROCEDURESDTC B125CCIRCUIT/SYSTEM TESTING
2019 GMC Sierra 1500 Limited Base, 4WD, Gas
Circuit/System Testing
2019 GMC Sierra 1500 Limited Base, 4WD, GasSECTION Circuit/System Testing
- Ignition 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.
- Ignition ON, radio tuned to XM channel 1.
- 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
- If DTC B125C is set as current or XM reception is not improved
- Ignition OFF, disconnect the digital radio antenna coax cable from the T4G Cellular Phone, Navigation, and Digital Radio Antenna.
- 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
- If the coax cable does not pass the test
- Test or replace the T4G Cellular Phone, Navigation, and Digital Radio Antenna.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.