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HOMESERVICE MANUALSGMC2024SIERRA 2500 HD DENALI ULTIMATEREPAIR AND DIAGNOSIS (SINGLE PAGE)ACCESSORIES & EQUIPMENTENTERTAINMENT SYSTEMSCELLULAR, ENTERTAINMENT, AND NAVIGATION - DIAGNOSTIC INFORMATION AND PROCEDURESDIAGNOSTIC INFORMATION AND PROCEDURESDTC B1B79CIRCUIT/SYSTEM TESTING
2024 GMC Sierra 2500 HD Denali Ultimate

Circuit/System Testing

2024 GMC Sierra 2500 HD Denali UltimateSECTION Circuit/System Testing
  1. Ignition OFF, disconnect the X1 harness connector at the A22 Radio Control.
  2. Test for less than 10 Ω between the ground circuit terminal 8 and ground.
    • If 10 Ω or greater 
    1. Ignition OFF.
    2. Test for less than 2 Ω in the ground circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, repair the open/high resistance in the ground connection.
    • Go to next step: If less than 10 Ω 
  3. Verify that a test lamp illuminates between the B+ circuit terminal 1 and ground.
    • If the test lamp does not illuminate and the circuit fuse is good. 
    1. Ignition OFF, remove the test lamp.
    2. Test for less than 2 Ω in the B+ circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, verify the fuse is not open and there is voltage at the fuse.
    • If the test lamp does not illuminate and the circuit fuse is open 
    1. Ignition OFF, remove the test lamp.
    2. Test for infinite resistance between the B+ circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance, replace the A22 Radio Control..
    • Go to next step: If the test lamp illuminates 
  4. Reconnect connect X1 at he A22 Radio Control.
  5. Verify the LVDS interface cable is properly connected at the A22 Radio Control and the A11 Radio and there is no damage to the cable or connections.
  6. Ignition ON/vehicle in service mode, infotainment system ON.
  7. Verify the A22 Radio Control displays an image.
    • If the A22 Radio Control does not display an image. 

      Replace LVDS interface cable from the A22 Radio Control to the A11 Radio.

    1. Ignition ON/vehicle in service mode, infotainment system ON.
    2. Verify the A22 Radio Control displays an image.
      • If the A22 Radio Control does not display an image.

        Replace the A22 Radio Control.

    3. Ignition ON/vehicle in service mode, infotainment system ON.
    4. Verify the A22 Radio Control displays an image.
      • If the A22 Radio Control does not display an image.

        Replace the A11 Radio.

      • Go to next step: If the A22 Radio Control displays an image

        Go to next step: A fault is currently not present and may be an intermittent condition.

    • Go to next step: If the A22 Radio Control displays an image. 
  8. A fault is currently not present and may be an intermittent condition.
RENDER: 1.0x

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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.