The brake light switch indicates brake pedal status to the ABS control unit. The switch is turned on when brake is applied. The brake light switch is a normally-open contact which runs to battery voltage when active (brake operated). When passive (brake not operated), the cable is grounded via the break light bulbs. The brake light switch is not monitored if the valve relay drops out, or in the event of low voltage or overvoltage.
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 of Brake Light Switch circuit ● Faulty Brake Light Switch ● Faulty input stage in HECU |
Monitoring Period | ● Continuous in the normal operating voltage range, with a filter time of 1s (after initialization has elapsed). | |
Enable Conditions | ● The stop lamp switch is a normally-open contact which runs to battery voltage when active (brake operated). When passive (brake not operated), the cable is grounded via the break light bulbs. Decoding is done in the control unit with BLS(brake light switch) depending parameters. When the line is broken, the control unit detects an intermediate level on the brake light switch line 40% of battery voltage < brake light switch voltage < 67% of battery voltage continued for 500msec, which is interpreted as a fault. | |
Fail Safe | ● ABS is not switched off. Fault recording for diagnostic purpose occurs immediately. The control unit is unable to detect the status of the brake light. ● The ABS and the EBD warning lamps are not activated. |
