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Home >> Buick >> 2015 >> Regal GS, AWD >> Repair and Diagnosis >> Accessories & Equipment >> Drivers Assistance Systems - ADAS >> Object Detection And Pedestrian Protection System >> Diagnostic Information and Procedures >> DTC B127B: Video Signal From Rearview Camera Not Received By Human Machine Interface Control Module >> Circuit/System Testing

Circuit/System Testing

  1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the B87 Rearview Camera. It may take up to 2 min for all vehicle systems to power down.
  2. Test for less than 10Ω between the ground circuit terminal 5 and ground.

      If 10Ω or greater 

    1. Ignition OFF.
    2. Test for less than 2Ω in the ground circuit end to end.

      If 2Ω or greater, repair the open/high resistance in the circuit.

      If less than 2Ω, repair the open/high resistance in the ground connection.

      If less than 10Ω 

  3. Ignition ON.
  4. Verify a test lamp illuminates between the ignition circuit terminal 6 and ground.

      If the test lamp does not illuminate and the circuit fuse is good 

    1. Ignition OFF.
    2. Test for less than 2Ω in the ignition circuit end to end.

      3. If 2Ω or greater, repair the open/high resistance in the circuit.

      If less than 2Ω, verify the fuse is good and there is voltage at the fuse. Refer to Power Mode Mismatch.

      If the test lamp does not illuminate and the circuit fuse is open 

    1. Ignition OFF.
    2. Test for infinite resistance between the ignition circuit and ground.

      3. If less than infinite resistance, repair the short to ground on the circuit.

      If infinite resistance, replace the B87 Rearview Camera.

      If the test lamp illuminates 

  5. Engine running, trunk/liftgate closed, park brake applied, transmission in R.
  6. Verify a test lamp illuminates between the control circuit terminal 3 and ground.

      If the test lamp does not illuminate 

    1. Ignition OFF.
    2. Test for infinite resistance between the ignition circuit and ground.

      3. If less than infinite resistance, repair the short to ground on the circuit.

      If infinite resistance

    3. Test for less than 2Ω in the ignition circuit end to end.

      4. If 2Ω or greater, repair the open/high resistance in the circuit.

      If less than 2Ω, refer to BACKUP LAMPS MALFUNCTION (AUTOMATIC TRANSMISSION) or BACKUP LAMPS MALFUNCTION (MANUAL TRANSMISSION) .

      If the test lamp illuminates 

  7. Ignition OFF, disconnect the X2 harness connector at the K74 Human Machine Interface Control Module, ignition ON.
  8. Test for less than 1 V between the signal circuit terminal listed below and ground:
    • K74 Human Machine Interface Control Module signal (+) circuit terminal 5 X2
    • K74 Human Machine Interface Control Module signal (-) circuit terminal 6 X2

    9. If 1 V or greater 

    Repair the short to voltage on the circuit.

    If less than 1 V 

  9. Ignition OFF.
  10. Test for infinite resistance between the signal circuit terminal listed below and ground:
    • K74 Human Machine Interface Control Module signal (+) circuit terminal 5 X2
    • K74 Human Machine Interface Control Module signal (-) circuit terminal 6 X2

      If less than infinite resistance 

      Repair the short to ground on the circuit.

      If infinite resistance 

  11. Test for less than 2Ω between the K74 Human Machine Interface Control Module signal (+) circuit terminal 5 X2 and the B87 Rearview Camera signal (+) circuit terminal 1

    12. If 2Ω or greater 

    Repair the open/high resistance in the circuit.

    If less than 2Ω 

  12. Test for less than 2Ω between the K74 Human Machine Interface Control Module signal (+) circuit terminal 6 X2 and the B87 Rearview Camera signal (+) circuit terminal 4

    13. If 2Ω or greater 

    Repair the open/high resistance in the circuit.

    If less than 2Ω 

  13. Replace the B87 Rearview Camera.
  14. Engine running, trunk/liftgate closed, park brake applied, transmission in R.
  15. Verify a clear rear vision image is displayed on the P17 Info Display Module.

    16. If a clear rear vision image is not displayed 

    Replace the K74 Human Machine Interface Control Module.

    If a clear rear vision image is displayed 

  16. All OK.
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