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Home >> Cadillac >> 2018 >> Escalade ESV Platinum, RWD >> Repair and Diagnosis >> Accessories & Equipment >> Exterior Lights >> Lighting System - DTC B0655 To DTC B3951 >> Diagnostic Information And Procedures >> DTC B258A: Low Beam Control Circuit >> Circuit/System Testing

Circuit/System Testing

  1. Ignition OFF, disconnect the X5 harness connector at the K9 Body Control Module.
  2. Connect a 3 A fused jumper between the control circuit terminal 13 and ground.
  3. Connect a test lamp between the F122UA fuse test point and ground, ignition on.
  4. Verify the test lamp turns ON and OFF while connecting and disconnecting the jumper wire
    • If the test lamp is always OFF 
    1. Disconnect the X4 harness connector at the X50A Fuse Block - Underhood.
    2. 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 X50A Fuse Block - Underhood.
    • If the test lamp is always ON 
    1. Disconnect the X4 harness connector at the X50A Fuse Block - Underhood.
    2. Test for infinite resistance between the control circuit terminal and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance, replace the X50A Fuse Block - Underhood.
    • Go to next step: If the test lamp turns ON and OFF 
    1. Disconnect the X4 harness connector at the X50A Fuse Block - Underhood.
    2. Test for less than 1 V between the control circuit terminal and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the K9 Body Control Module.
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