Brake Lamp: Description and Operation

Brake Lights

The brake lights go on when the brake light switch is actuated.
The brake light switch is powered with +30 When the brake pedal is depressed, the brake light switch closes and pin 48 on TWICE receives current. TWICE monitors each brake light circuit separately and outputs information to the bus, which is used by SID.

Current from TWICE goes to the following pins:
^ pin 25 for the LH brake light.
^ pin 1 for the RH brake light.
^ pin 24 for the high-level brake light.

Open circuit
The current to each pin in TWICE passes through a shunt resistor. If there is a fault in the circuit, e.g. a broken filament, the shunt resistor becomes unbalanced. The TWICE control module detects this imbalance and outputs error information to the bus. SID read this information and displays a message.