Put the Electronic Parking Brake into Service Mode

The BMW 2 Series Coupe (G42, 2021–Present) is rear-wheel-drive on BMW’s CLAR architecture and uses an electromechanical parking brake with electric motors mounted on the two rear calipers. Because those motors hold the rear pistons, a rear pad change starts not with a wind-back tool but by putting the EPB into service (maintenance) mode so it retracts the pistons electronically. There is no accelerator-and-switch owner sequence on the G42 — it is a tool-led job, with a manual fallback if you have no scanner.

What service mode is and why the G42 needs it

Each rear caliper carries a geared motor that drives the parking-brake piston. With the car live, that motor clamps the piston and resists being pushed back. Service mode commands both rear motors to wind fully open and locks the EPB out so it cannot re-apply while your hands are at the caliper. Only then can the pistons be compressed and the new pads fitted.

Retracting the rear calipers on the G42

Park on level ground, chock a front wheel, and connect a battery charger — the motors draw current and low voltage can abort the cycle. Then pick a route:

1. Scan-tool route (recommended). Plug a BMW-capable tool into the OBD port under the dash: BMW ISTA / Rheingold is the factory option, and consumer tools such as BimmerLink, Foxwell or a Schwaben/Autel EPB unit also carry the function. Open the parking-brake service menu and follow the prompts to retract; you’ll hear the rear motors whir as the pistons wind open.
2. Manual route (no tool). Confirm the EPB is released, unbolt the actuator motor (two Torx screws) from the back of each rear caliper, insert a Torx bit into the spindle and turn it clockwise until it stops to wind the piston in. Refit the motors before driving.

With the pistons home, compress them fully, fit the new pads and refit the caliper.

Never force the pistons back by hand

Never push or lever the G42’s rear EPB pistons back with a clamp or wind-back tool while the actuator is attached. They are electromechanical — driving one back through its motor shears the gearset inside and destroys the caliper. Retract the piston electronically in service mode, or only ever by turning the spindle clockwise with the actuator removed. If a piston feels solid, the car is not in service mode — stop and re-run the routine instead of forcing it.

Exit, CBS reset and bed-in

Once the pads are in and the wheels back on, end service mode with the tool (or pump the brake pedal firmly several times then apply the EPB switch once) so the motors re-clamp to the correct air gap. A good sequence is to leave the tool connected, turn the ignition off, then pump the pedal until it is firm before moving the car. While the tool is connected, reset the rear-brake CBS (Condition Based Service) counter in ISTA/BimmerLink so the dash stops counting the old pads. Then bed the pads in: several firm slow-downs from about 30 mph with cooling between them, and check the parking brake holds on a slope.

Frequently Asked Questions

Can I change G42 rear pads without a scan tool? Yes, by the manual route — release the EPB, unbolt each rear actuator and wind the spindle in clockwise with a Torx bit. You’ll still want a tool (ISTA or BimmerLink) afterwards to reset the rear-brake CBS reminder cleanly.

Will the M240i be any different? The M240i uses the same electromechanical rear calipers and the same service-mode procedure; larger brakes don’t change the method, only the pad part numbers.

Do the pistons screw in or push straight? The rear EPB pistons wind in clockwise; they don’t push straight like the fronts. With the actuator off, turn the spindle clockwise on each side.

Service mode aborted partway — why? Usually low battery voltage. Put the G42 on a charger and retry; the EPB motors need a strong 12 V supply to complete a retract.

If the dash throws a brake or EPB fault code while you work, decode it first on our sister site autodtcs.com.