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Home >> GMC >> 2018 >> Terrain SL >> Repair and Diagnosis (Single Page) >> Electrical >> Charging Systems >> 12 V Starting And Charging System >> Diagnostic Information And Procedures >> DTC P156D: DC/DC Converter Ignition Switch Run/Start Position Signal Message Counter Incorrect >> Circuit/System Testing
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Circuit/System Testing

  1. Verify that no other DTCs are set except for DTC P156D.
    • Go to next step: If only DTC P156D is set 
  2. Replace the T19 Power Supply Transformer.
  3. Verify the DTC does not set while operating the vehicle within the Conditions for Running the DTC.
    • If DTC sets 

      Replace the K20 Engine Control Module.

    • Go to next step: If DTC does not set 
  4. All OK.
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