Electric parking brake (EPB)
Definition
The electric parking brake replaces the handbrake lever with a switch: either small electric motors with a gearbox on each rear caliper press the piston via a spindle (motor-on-caliper), or a central actuator pulls conventional cables. The EPB module monitors motor current to judge clamping force, releases automatically when driving off, applies on shutdown if configured, and performs an emergency brake if the switch is pulled while moving. Before changing rear pads the pistons must be retracted into service mode with a scan tool or by the car's own service menu; forcing them back damages the spindle. Faults are motors that burn out or seize from water ingress, worn gear sets that click or whine without clamping, corroded connectors behind the wheels, cables that stretch or freeze on central units, and a switch that fails; low battery voltage during actuation also triggers faults. Symptoms are a flashing or steady parking brake lamp, EPB fault messages, a brake that will not release or will not hold, and a buzzing from one rear wheel. Codes: C1Axx-series and manufacturer codes (VAG 01435/02432/C10xx, BMW 480A-480E, Ford C1A00-series, Mercedes C1120), U0128 (lost communication with park brake module).