P0504
PowertrainBrake Systemmoderate severityBrake Switch A/B Correlation
What P0504 Means
The two brake light switch signals disagree with each other. The PCM can't confirm whether the brake pedal is truly pressed.
Symptoms
- Check engine light on
- Cruise control won't engage
- Erratic brake lights
Common Causes
- Faulty brake light switch
- Misadjusted brake switch
- Wiring fault between switches
- Poor connector contact
Diagnostic Steps
- Scan for brake switch data
- Check brake switch adjustment
- Compare both switch signals on scan tool
- Inspect brake switch wiring and connectors
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