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Home >> Chevrolet >> 2024 >> Tahoe Commercial, 4WD >> Repair and Diagnosis >> Accessories & Equipment >> Anti-Theft Systems >> Power Door Locks And Vehicle Access - Diagnostic Information And Procedures (2 Of 2) >> 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 150 or the ground connection.
    • Go to next step: If the test lamp illuminates 
  3. Ignition ON, Vehicle in Service Mode.
  4. Test for 4.8 - 5.2V between the signal circuit terminal 1 and ground.
    • If less than 4.8V 
    1. Ignition/Vehicle - Off.
    2. Disconnect the electrical connector: X1 at the K20 Engine Control Module.
    3. 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
    4. 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.
    5. Replace the K20 Engine Control Module.
    • If greater than 5.2V 
    1. Ignition/Vehicle - Off.
    2. Disconnect the electrical connector: X1 at the K20 Engine Control Module.
    3. Ignition ON, Vehicle in Service Mode.
    4. Test circuit 4063 for a short to voltage.
      • If a short to voltage is found, repair the fault on the circuit.
      • Go to next step: If a short to voltage is not found.
    5. Replace the K20 Engine Control Module.
    • Go to next step: If between 4.8 - 5.2V 
  5. Test or replace the B55 Engine Compartment Cover Switch.
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