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Home >> Buick >> 2021 >> Envision Preferred, AWD >> Repair and Diagnosis >> Body & Frame >> Body, Cab Control Systems >> Vehicle Access System >> Diagnostic Information and Procedures >> DTC P257D-P257F >> Circuit/System Testing

Circuit/System Testing

  1. Vehicle OFF and all vehicle systems OFF, disconnect the harness connector at the B55 Engine Compartment Cover Switch.
  2. Verify a test lamp illuminates between ground circuit terminal 3 and B+.
    • If the test lamp does not illuminate 
    1. Repair the open/high resistance on circuit 1150 or the ground connection.
    • Go to next step: If the test lamp illuminates 
  3. Ignition ON, Vehicle in Service Mode
  4. Test for greater than 12 V between the signal circuit terminal 1 and ground
    • If 12 V or less 
    1. Test circuit 4063 for a short to ground.
      • If a short to ground is found, repair the fault on the circuit.
      • Go to next step: If a short to ground is not found
    2. Test circuit 4063 for an open/high resistance.
      • If an open/high resistance is found, repair the fault on the circuit.
      • Go to next step: If an open/high resistance is not found.
    3. Replace the K20 Engine Control Module.
    • Go to next step: If greater than 12 V 
  5. Test or replace the B55 Engine Compartment Cover Switch.
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