P0504 - Brake Switch A/B Correlation

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

Treat the code as the starting point: compare symptoms, likely causes, and repair paths before pricing parts or moving into an estimate.

Code Overview

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

Common Causes

• Failed sensor or idle control component
• Damaged wiring or connector
• Throttle body or switch issue

Diagnostic Steps

1. Inspect the related connector and harness
2. Compare live data to vehicle behavior
3. Check for mechanical sticking or adjustment problems

Likely Repairs & Cost Guides

Use symptoms, scan data, and quick checks to confirm the likely repair path before pricing parts. The estimator helps compare repair paths before replacing anything unnecessarily.

Related OBD Codes

Browse nearby code-family pages when the same fault pattern overlaps across systems, such as misfire, lean fuel trim, EVAP sealing, cooling, or charging faults.

Next Steps

Move from code lookup to diagnosis, then estimate the likely repair only after symptoms, causes, and checks point to the same path.