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Home >> Buick >> 2016 >> Encore Base, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 45 (Lighting System) >> Diagnostic Information and Procedures >> DTC B257B: Lighting Control Switch >> Circuit/System Testing
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Circuit/System Testing

WARNING: This page is about a different car, the 2015 Chevrolet Trax and 2015 Buick Encore. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the S30 Headlamp Switch, ignition ON.
  2. Test for B+ between the B+ circuit terminal 1 and ground.
    • If less than B+ 
    1. Ignition OFF, disconnect the X3 harness connector at the K9 Body Control Module.
    2. Test for infinite resistance between the B+ circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance
    3. Test for less than 2 Ω in the B+ circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the K9 Body Control Module.
    • If B+ 
  3. Verify a test lamp does not illuminate between the B+ circuit terminal 1 and the signal circuit terminal 12.
    • If the test lamp illuminates 
    1. Ignition OFF, disconnect the X1 harness connector at the K9 Body Control Module.
    2. Test for infinite resistance between the signal circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance, replace the K9 Body Control Module.
    • If the test lamp does not illuminate 
  4. Test for B+ between the B+ circuit terminal 1 and the signal circuit terminal 12.
    • If less than B+ 
    1. Ignition OFF, disconnect the X1 harness connector at the K9 Body Control Module, ignition ON.
    2. Test for less than 1 V between the signal circuit terminal 12 and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V
    3. Test for less than 2 Ω in the signal circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the K9 Body Control Module.
    • If B+ 
  5. Test or replace the S30 Headlamp Switch.