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Home >> Cadillac >> 2007 >> Escalade EXT >> Repair and Diagnosis >> External Pages >> Different car >> Section 1599 (Lighting System) >> Diagnostic Information and Procedures >> DTC B2580 >> Circuit/System Testing
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Circuit/System Testing

WARNING: This page is about a different car, the 2010 GMC Sierra, 2010 GMC Cab & Chassis Sierra, 2010 Chevrolet Silverado, and 2010 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, disconnect the X4 harness connector at the fuse block - underhood.
  2. Connect a test lamp between the control circuit terminal C3 and B+.
  3. Command the High Beams ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
    • If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the BCM.
    • If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.
  4. Ignition OFF, connect the X4 harness connector at the fuse block - underhood. Disconnect the harness connector at the high beam headlamp.
  5. Test for less than 5 Ω between the high beam headlamp ground circuit terminal B and ground
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  6. Connect a test lamp between the control circuit terminal A and ground.
  7. Command the High Beams ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
    • If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the fuse block - underhood.
    • If the test lamp is always OFF and the circuit fuse is good, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the fuse block - underhood.
    • If the test lamp is always OFF and the circuit fuse is open, test the control circuit for a short to ground. If the circuit tests normal, test or replace the high beam headlamp.
  8. If all circuits test normal, test or replace the high beam headlamp.
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