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HOMESERVICE MANUALSPONTIAC2008GRAND PRIX BASEREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 243 (LIGHTING)DIAGNOSTIC INFORMATION AND PROCEDURESDTC B2580CIRCUIT/SYSTEM TESTING
2008 Pontiac Grand Prix Base

Circuit/System Testing

2008 Pontiac Grand Prix BaseSECTION Circuit/System Testing
WARNING: This page is about a different car, the 2008 Hummer H2. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, disconnect the harness connector X4 at the BCM.
  2. Low beam headlamps ON, verify the high beam headlamps are not on.
    • If the high beam headlamps are on, test the high beam relay control circuit for a short to ground. If the circuit tests normal replace the underhood fuse block.
  3. Install a 10A fused jumper wire between the relay control circuit terminal 16 and ground. Verify the high beam headlamps are on.
    • If the high beam headlamps are not on, test the high beam relay control circuit for a short to voltage or an open/high resistance. If the circuit tests normal replace the underhood fuse block.
  4. If all circuits test normal, replace the BCM.
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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.