The brief
Jolene's X4 wouldn't move despite her stepping on the accelerator, with a parking brake warning on the dash. He brought it in. When the car won't roll and the parking brake won't release, that's the electric parking brake stuck on. The electric parking brake uses an actuator, a motor and gearbox that pulls the brake on and off, either built into the rear calipers or as a central unit driving cables, with a control module behind it. The actuator's motor and gears wear, so it stops releasing cleanly, and when it jams on, the car can't move. A failed parking brake actuator doesn't recover, so it needs replacing, then coded to the car and the system reset and recalibrated.
The diagnosis
A diagnostic scan pulled the fault to the parking brake actuator, jammed on and not releasing, which is exactly why the car wouldn't move. The rear brakes themselves and the wiring checked out, it was the actuator at fault. That's an actuator replacement, you don't rebuild it on the car, so the call was a complete unit, fitted, coded to the car, and the parking brake system reset and recalibrated through the proper procedure.
The work
The old parking brake actuator was removed and a new genuine BMW-spec unit fitted, connected up, every fastener torqued to spec. The new actuator was coded to the car so the module recognised it, the parking brake system reset and recalibrated through the proper procedure, and the stored faults cleared. A check confirmed the parking brake applied and released reliably from the switch, held the car firmly, released cleanly, and the car rolled freely with the warning gone.
The outcome
An electric parking brake that applies and releases reliably, holds the car firmly, releases cleanly so the car moves, and does it without a warning on the dash. The X4 went home with the parking brake sorted. A jammed-on parking brake leaves the car going nowhere, so changing the actuator, coding it in and resetting the system put it right.
