P0504

Brake Switch A/B Correlation

Severity

⚠️ Medium

Can you drive?

Limited driving only, diagnose soon

Approx. repair cost

$22–56 (est.)

Symptoms

Incorrect operation of brake lights
Problems with cruise control
Difficulty starting the engine
Incorrect operation of the ABS system

Causes

Brake pedal sensor malfunction
Open or short circuit in wiring harness
Contact corrosion
Problems with the engine control unit (ECU)

How to Fix

Check the condition of the brake pedal sensor
Inspect the wiring harness for damage
Check contacts for corrosion
Test the operation of sensor circuits A and B
If necessary, replace the sensor or repair the wiring harness

Related codes

P0500 P0501 P0502 P0503