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Home >> Kia >> 2016 >> Optima SX Limited >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 108 (Engine Control System Diagnosis - 1.6L (2 Of 3) - Optima (Except HEV)) >> DTC P0504: Brake Switch "A"/"B" Correlation >> Wiring Inspection >> Signal Circuit Inspection

Signal Circuit Inspection

WARNING: This page is about a different variant/trim than selected.
  1. Ignition "OFF" and disconnect ECM connector.
  2. Ignition "ON" and keep the brake taking off.
  3. Measure voltage between Pin No. 3 (brake switch signal) terminal of brake switch harness connector and chassis ground.
  4. Measure voltage between Pin No. 1 (brake lamp signal) terminal of brake switch harness connector and chassis ground.

    Specification: 

    Brake Switch - Approx 12V

    Brake lamp Switch - 0V

  5. Keep the brake stepping on.
  6. Measure voltage between Pin No. 3 (brake switch signal) terminal of brake switch harness connector and chassis ground.
  7. Measure voltage between Pin No. 1 (brake lamp signal) terminal of brake switch harness connector and chassis ground.

    Specification: 

    Brake Switch - 0V

    Brake lamp Switch - Approx 12V

    Item During taking off the brake During stepping on the brake
    Brake Switch 0V Battery voltage
    Brake lamp Switch Battery voltage 0V
  8. Is the measured voltage within specification?

    YES 

    • If problem still occurs, replace brake switch and then go to "SYSTEM INSPECTION " procedure.

    NO 

    • Check the fuse between battery and stop lamp switch.
    • Repair open or short in power circuit of stop lamp switch and go to "VERIFICATION OF VEHICLE REPAIR " procedure.