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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 B258A >> 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 harness connector at the appropriate E4 low beam headlamp.
  2. 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.
  3. Connect a test lamp between the control circuit terminal A and the ground circuit terminal B.
  4. Command Headlamp Low Beam 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 K9 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 K9 BCM.
  5. If all circuits test normal, test or replace the E4 low beam headlamp.
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