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Home >> GMC >> 2011 >> Terrain SLT, 2.4 C, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 178 (Lighting System) >> Diagnostic Information and Procedures >> DTC B2580 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2010 GMC Terrain and 2010 Chevrolet Equinox. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, disconnect the KR48 Headlamp High Beam Relay.
  2. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 30 and ground.
    • If the test lamp illuminates, test the control circuit for a short to voltage.
  3. Verify that a test lamp illuminates between the B+ circuit terminal 86 and ground.
    • If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
  4. Verify that a test lamp illuminates between the B+ circuit terminal 87 and ground.
    • If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.
  5. Disconnect the harness connector at the appropriate E4 Headlamp - High Beam.
  6. Test for less than 5 Ω between the ground circuit terminal B and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  7. Connect the harness connector at the E4 Headlamp - High Beam.
  8. Connect a 10 A fused jumper wire between the B+ circuit terminal 87 and the control circuit terminal 30. Verify the E4 Headlamp - High Beam is activated.
    • If the E4 Headlamp - High Beam does not activate and the circuit fuse is good, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the E4 Headlamp - High Beam.
    • If the E4 Headlamp - High Beam does not activate and the circuit fuse is open, test the control circuit for a short to ground. If the circuit tests normal, test or replace the headlamp.
  9. Connect a test lamp between the B+ circuit terminal 86 and the control circuit terminal 85.
  10. Turn the high beam headlamps ON and OFF using the S78 Turn Signal/Multi-Function Switch. The test lamp should turn ON and OFF when changing between the selected states.
    • If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the K9 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 K9 BCM.
  11. If all circuits test normal, test or replace the KR48 Headlamp High Beam Relay.
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