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Home >> GMC >> 2021 >> Terrain SL >> Repair and Diagnosis >> External Pages >> Different car >> Section 94 (Driver Assistance Systems) >> Diagnostic Information And Procedures >> DTC B0987 (GMC) >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2020 GMC Terrain and 2020 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 S126 Drive Mode Select Switch, ignition ON.
    2. NOTE:

    Verify interior light dimming is turned all the way up.

  2. Verify a test lamp illuminates between the control circuit terminal 8 and ground.
    • Go to next step: If the test lamp illuminates 
  3. Ignition OFF, connect the harness connector at the S126 Drive Mode Select Switch. Disconnect the harness connector at the B174W Frontview Camera - Windshield, ignition ON.
  4. Verify the lane keep assist indicator is not illuminated.
    • If the lane keep assist indicator is illuminated 
    1. Ignition OFF, disconnect the harness connector at the S126 Drive Mode Select Switch.
    2. Test for infinite resistance between the control circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance, replace the S126 Drive Mode Select Switch.
    • Go to next step: If the lane keep assist indicator is not illuminated 
  5. Connect a 3 A fused jumper wire between the control circuit terminal 4 and ground
  6. Verify the lane keep assist indicator is illuminated.
    • If the lane keep assist indicator is not illuminated 
    1. Ignition OFF, disconnect the harness connector at the S126 Drive Mode Select Switch, ignition ON.
    2. Test for less than 1 V between the control circuit and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • Go to next step: If less than 1 V
    3. Ignition OFF.
    4. Test for less than 2 Ω in the control circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the S126 Drive Mode Select Switch.
    • Go to next step: If the lane keep assist indicator is illuminated 
  7. Test or replace the B174W Frontview Camera - Windshield.
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