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 B2740CIRCUIT/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 ON, verify that a test lamp illuminates between the 12 V reference circuit terminal 1 and ground.
- If the test lamp does not illuminate, test the 12 V reference circuit for a short to ground or an open/high resistance. If the circuit tests normal and the circuit fuse is open, test the signal circuit terminal 12 for a short to ground.
- Verify the scan tool Front Fog Lamps Switch parameter is Inactive.
- If not the specified value, test the signal circuit terminal 12 for a short to voltage. If the circuit tests normal, replace the K9 BCM.
- Install a 3 A fused jumper wire between the signal circuit terminal 12 and the 12 V reference circuit terminal 1. Verify the scan tool Front Fog Lamps Switch parameter is Active.
- If not the specified value, test the signal circuit for 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:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.