Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSBUICK2013REGAL TURBO PREMIUM, STANDARD TRANSREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 150 (LIGHTING SYSTEM)DIAGNOSTIC INFORMATION AND PROCEDURESDTC B257ACIRCUIT/SYSTEM TESTING
2013 Buick Regal Turbo Premium, Standard Trans
Circuit/System Testing
2013 Buick Regal Turbo Premium, Standard TransSECTION Circuit/System Testing
WARNING: This page is about a different car, the 2012 Buick Regal. However, it is still accessible from the selected car via links, so may be relevant.
- Ignition OFF, disconnect the harness connector at the S30 headlamp switch.
- Ignition OFF, test for less than 30 Ξ© between the ground circuit terminal 6 and ground.
- If greater than the specified range, test the ground circuit for an open/high resistance.
- Ignition ON, verify the scan tool Park Lamps Switch parameter is Inactive.
- If not the specified value, test the signal circuit terminal 3 for a short to ground. If the circuit tests normal, replace the K9 BCM.
- Install a 3 A fused jumper wire between the signal circuit terminal 3 and the ground circuit terminal 6. Verify the scan tool Park Lamps Switch is Active.
- If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K9 BCM.
- Verify the scan tool Headlamps On Switch parameter is Inactive.
- If not the specified value, test the signal circuit terminal 4 for a short to ground. If the circuit tests normal, replace the K9 BCM.
- Install a 3 A fused jumper wire between the signal circuit terminal 4 and the ground circuit terminal 6. Verify the scan tool Headlamps On Switch is Active.
- If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K9 BCM.
- Verify the scan tool Automatic Headlamps Disable Switch parameter is Inactive.
- If not the specified value, test the signal circuit terminal 5 for a short to ground. If the circuit tests normal, replace the K9 BCM.
- Install a 3 A fused jumper wire between the signal circuit terminal 5 and the ground circuit terminal 6. Verify the scan tool Automatic Headlamps Disable Switch is Active.
- If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K9 BCM.
- If all circuits test normal, test or replace the S30 headlamp switch.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- β’ You smell fuel, burning insulation, or see smoke.
- β’ Brakes feel soft, pull hard to one side, or make grinding noises.
- β’ The engine overheats, stalls repeatedly, or misfires under load.
- β’ You are missing required tools, torque specs, or safe lifting equipment.
- β’ You are not confident in the next step or safety outcome.