P0504 — Brake Switch A/B Correlation

P0504: Brake Switch A/B Correlation — what it means, the affected system and what to check before replacing parts.

Meaning, symptoms, causes and checks

Brake Switch A/B Correlation. Basic catalogue definition; diagnostic details have not yet been reviewed.

Affected system: Powertrain

Symptoms

  • Brake lamps off or continuously lit; cruise control unavailable.

Possible causes

  • Faulty brake switch, incorrect adjustment or damaged wiring.

What to check

  • Check brake lamps, fuses, connectors and switch adjustment against service information.

Also written as: P0504-00, P050400, PO504 (some scan tools add the fault-type byte, e.g. -00).