P0504 – Brake Switch A/B Correlation

Description

The ECM detects a mismatch between brake switch A and B signals.

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Symptoms

  • Brake lights not working
  • Cruise control inoperative
  • ABS light on

Causes

  • Faulty brake switch
  • Misadjusted switch
  • Wiring issues

Diagnosis

  • Monitor brake switch data
  • Inspect switch
  • Check wiring

Repair

  • Replace brake switch
  • Adjust switch
  • Repair wiring