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HOMESERVICE MANUALSGMC2009CANYON 4D PICKUP, 2.9 9REPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 3 (LIGHTING SYSTEMS)DIAGNOSTIC INFORMATION AND PROCEDURESDTC B2575CIRCUIT/SYSTEM TESTING
2009 GMC Canyon 4D Pickup, 2.9 9

Circuit/System Testing

2009 GMC Canyon 4D Pickup, 2.9 9SECTION Circuit/System Testing
WARNING: This page is about a different car, the 2008 Isuzu i-370, 2008 Isuzu i-290, 2008 GMC Canyon, and 2008 Chevrolet Colorado. However, it is still accessible from the selected car via links, so may be relevant.

Headlamp Relay Control Circuit Test

  1. Ignition OFF, disconnect the headlamp relay.
  2. Connect a test lamp between the relay coil control circuit terminal 86 and battery voltage.
  3. Ignition ON, command the headlamps on and off with a scan tool and verify that the test lamp turns on and off.
    • If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.
    • If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
  4. If all circuits test normal, test or replace the relay.
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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.