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Home >> Chevrolet >> 2012 >> Traverse LS, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 8 (Lighting System) >> Diagnostic Information and Procedures >> DTC B257B >> Circuit/System Testing
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Circuit/System Testing

WARNING: This page is about a different car, the 2010 Cadillac SRX. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, disconnect the harness connector at the S30 Headlamp Switch.
  2. Ignition ON, test for B+ between the B+ reference circuit terminal 1 and ground.
    • If less than the specified range, test the B+ reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K9 BCM.
  3. Ignition ON, test for less than 0.3 V between signal circuit terminal 12 and ground.
    • If greater than the specified range, test the signal circuit terminal 12 for a short to voltage. If the circuit tests normal, replace the K9 BCM.
  4. Reconnect the harness connector at the S30 Headlamp Switch.
  5. Dim the interior backlighting with the S30 Headlamp Switch.
  6. Disconnect the harness connector at the S30 Headlamp Switch.
  7. Install a 3 A fused jumper wire between the signal circuit terminal 12 and the B+ reference circuit terminal 1. The interior backlighting should now be dimmed.
    • If the interior backlighting is not dimmed, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K9 BCM.
  8. If all circuits test normal, replace the S30 Headlamp Switch.
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