The brake light switch indicates brake pedal status to the ABS control unit. The switch is turned on when brake is depressed. The brake light switch is a normally-open contact which runs to battery voltage when active (brake depressed). When passive (brake not depressed), the cable is grounded via the break light bulbs.
The brake light signal is a reference to judge driver’s will for braking. ABS ECU monitor open circuit of brake light switch for normal ABS control.
Item
Detecting Condition
Possible cause
DTC Strategy
? Open circuit monitoring
? Open circuit in brake switch line
? Faulty brake light switch
? Faulty input stage in HECU
Detect Mode
? Initial Check
? Outside the ABS control cycle
? Inside the ABS control cycle
? Diagnosis mode
? Failure mode
Enable Conditions
? If both BLS(brake lamp switch) and BS(brake switch) have a same state for predetermined time, the failure is recognized.
Fail Safe
? Inhibit the TCS/ESP control and allow the ABS/EBD control.
? The TCS/ESP warning lamps are activated.