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Home >> Cadillac >> 2016 >> XTS Base >> Repair and Diagnosis >> Engine Performance >> System >> Data Communication System >> Diagnostic Information and Procedures >> DTC U0028: MOST Bus >> Circuit/System Verification
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Circuit/System Verification

  1. Ignition ON. Radio ON.
  2. If equipped, verify that the A33 Media Disc Player is operative by inserting or ejecting a disk.
    • If the disk can not be inserted or ejected 

      Test the power, ground, and serial data circuits of the A33 Media Disc Player for an open/high resistance.

    • If the disk can be inserted or ejected 
  3. Verify that the scan tool communicates with each MOST device, except the A33 Media Disc Player.
    • If any MOST device does not communicate with the scan tool 

      Refer to DTC U0100-U02FF  to diagnose power, ground, and serial data circuits of that MOST device.

    • If all MOST devices communicate with the scan tool 
  4. Verify that DTC U2098 or DTC U0029 02 is not set.
    • If any of the DTCs are set 

      Refer to DTC U2098 .

    • If none of the DTCs are set 
  5. Verify that DTC U0028 is not set.
    • If the DTC U0028 is set 
    1. Using the scan tool, select the MOST Bus Diagnostic Starting Point function from A11 Radio Control Functions menu.
    2. Determine the fault location from A11 Radio scan tool Control Functions, MOST Bus Diagnostic Starting Point. Reference Node Locations of MOST Bus Communication Break parameter value.
    3. Refer to Circuit/System Testing.
    • If the DTC U0028 is not set 
  6. Refer to Repair Verification.
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