Vehicle Safety
Recalls Search 320,000+ NHTSA safety recalls Complaints 2.1M+ consumer safety complaints TSBs 4.7M technical service bulletins VIN Lookup Decode any vehicle VIN instantly OBD Codes 12,000+ diagnostic trouble codes Fuel Economy EPA MPG data for all vehicles Safety Ratings 11,700+ NHTSA crash test ratings Investigations 5,300+ NHTSA defect investigations Statistics Recall trends & safety analysis
Consumer Safety
Product Safety 9,700+ CPSC product recalls Food Safety 28,600+ FDA food recalls Pet Safety 1.3M FDA animal adverse events Drug Safety 17,500+ FDA drug recalls Device Safety 38,400+ FDA device recalls Workplace Safety 102,900+ OSHA injury reports Brand History Cross-category recall lookup by company
Infrastructure
Bridge Safety 624,000 bridge inspections Aviation Safety 30,000+ NTSB aviation events Dam Safety 92,600 dam safety records Water Safety 433,000+ public water systems Railroad Safety 438,000+ rail crossings Pipeline Safety 8,800+ pipeline incidents State Safety Dashboards Safety grades for all 50 U.S. states ZIP Safety Report Check any 5-digit ZIP across 9 datasets
Public Health
Nursing Homes 14,700 CMS rated facilities Environmental 80,000+ hazardous sites & releases
Blog

Vehicle Safety

Vehicle Recalls320,000+ NHTSA safety recalls Browse VehiclesEvery make, model and year Complaints2.1M+ consumer safety complaints TSBs4.7M technical service bulletins VIN LookupDecode any vehicle VIN instantly OBD Codes12,000+ diagnostic trouble codes Fuel EconomyEPA MPG data for all vehicles Safety Ratings11,700+ NHTSA crash test ratings Investigations5,300+ NHTSA defect investigations StatisticsRecall trends & safety analysis Compare VehiclesTwo vehicles side by side

Consumer Safety

Product Safety9,700+ CPSC product recalls Food Safety28,600+ FDA food recalls Pet Safety1.3M FDA animal adverse events Drug Safety17,500+ FDA drug recalls Device Safety38,400+ FDA device recalls Workplace Safety102,900+ OSHA injury reports Brand HistoryRecall lookup by company

Infrastructure

Bridge Safety624,000 bridge inspections Aviation Safety30,000+ NTSB aviation events Dam Safety92,600 dam safety records Water Safety433,000+ public water systems Railroad Safety438,000+ rail crossings Pipeline Safety8,800+ pipeline incidents State DashboardsSafety grades for all 50 states ZIP ReportAny 5-digit ZIP across 9 datasets

Public Health

Nursing Homes14,700 CMS rated facilities Environmental80,000+ hazardous sites & releases BlogGuides, news & safety insights

OBD Code P0504

Brake Switch A/B Correlation

CodeP0504
DescriptionBrake Switch A/B Correlation
Possible CausesMisadjusted brake switch; Faulty switch; Wiring
SymptomsCruise control inop; Brake lights stuck on/off
SystemSpeed/Idle

What Does P0504 Mean?

Brake Switch A/B Correlation. This diagnostic trouble code (DTC) is stored when the vehicle's onboard computer detects an issue with the speed/idle.

Code Breakdown

P = Powertrain code

0 = Generic (SAE standard)

How to Fix P0504

Follow these diagnostic steps to identify and resolve the issue. Always start with the simplest checks before moving to more involved repairs.

  1. Check brake fluid level in the master cylinder reservoir — top off if low.
  2. Inspect brake pads and rotors for wear.
  3. Look for brake fluid leaks at calipers, wheel cylinders, brake lines, and master cylinder.
  4. Check the brake light switch for proper operation and adjustment.
  5. Inspect ABS sensor wiring if the code involves the ABS system.
  6. Bleed the brake system if air has entered the lines.
  7. Clear codes and test brake feel and stopping power.

Note: These are general diagnostic guidelines. Some vehicles may have model-specific procedures. Always consult your vehicle's service manual for exact specifications and torque values. If you are not comfortable performing these steps, visit a qualified mechanic.

Frequently Asked Questions

Is P0504 serious?

The severity depends on the underlying cause. Some triggers for P0504 are minor (like a loose gas cap), while others may indicate a more significant problem. We recommend having the code diagnosed with a proper scan tool to determine the exact cause before deciding on urgency.

Can I clear P0504 myself?

You can clear any OBD-II code with a code scanner or by disconnecting the battery for 15-30 minutes. However, clearing the code without fixing the underlying problem will cause it to return, usually within one or two drive cycles. If the code triggered the check engine light, the light will come back on. Fix the root cause first, then clear the code.

How much does it cost to fix P0504?

Repair costs vary widely depending on the root cause. Some fixes are free (like tightening a gas cap) while others can cost several hundred dollars (like replacing a catalytic converter or oxygen sensor). A proper diagnosis with a professional scan tool, not just reading the code, is the first step to getting an accurate repair estimate. Many auto parts stores offer free code reading, but a thorough diagnosis usually requires a mechanic.

View All OBD Codes