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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 B3890 >> 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 X2 harness connector at the X50A underhood fuse block.
  2. Connect a test lamp between the control circuit terminal K1 and B+.
  3. Turn the headlamp switch between the OFF and park light positions. 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 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 K9 BCM.
  4. Ignition OFF, connect the X2 harness connector at the X50A underhood fuse block.
  5. Test for less than 5 Ω between the X88 Trailer Connector ground circuit terminal D 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 B and ground.
  7. Turn the headlamp switch between the OFF and park light positions. 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 X88 Trailer Connector.
    • 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 X88 Trailer Connector.
    • 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 X88 Trailer Connector.
  8. If all circuits test normal, test or replace the X50A underhood fuse block.
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