Circuit/System Testing

2011 GMC Savana Special 4.8 ASECTION Circuit/System Testing
  1. Ignition OFF, disconnect the X3 harness connector at the BCM
  2. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 3 and ground.
    • If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open high/resistance.
  3. Ignition OFF, connect the X3 harness connector at the BCM and disconnect the harness connector at the headlamp switch.
  4. Ignition ON, verify that a test lamp illuminates between the B+ reference circuit terminal 15 and ground.
    • If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit test normal, replace the BCM.
  5. Ignition OFF, disconnect the harness connector at the stop lamp switch.
  6. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal C and ground.
    • If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.
  7. Install a 3A fused jumper wire between the signal circuit terminal D and the B+ circuit terminal C. Verify that the scan tool Stop Lamp Switch Status parameter is 1023 counts.
    • If not the specified value, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
  8. If all circuits test normal, replace the 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.