Brake Switch "A" Circuit Malfunction
The brake light switch signal seen by the ECU is implausible — for example, both contacts active simultaneously, or no signal change despite the brake pedal being pressed (cruise control engages and disengages on this signal). On many cars also disables shift interlock.
Affected components
- Brake light switch
- Brake light switch wiring
Common causes
- High likelihood: Brake switch failed (worn contacts, internal break)
- Medium likelihood: Switch misadjusted (does not actuate at correct pedal position)
Diagnostic notes
- The malfunction indicator lamp may illuminate
Sources
Diagnostic information is provided for reference only. Confirm the code with a compatible scan tool and follow the vehicle manufacturer's service procedures before replacing components.