Put the Electronic Parking Brake into Service Mode

Last updated: June 11, 2026

The BMW 1 Series (F40, 2019–Present) is BMW’s front-wheel-drive UKL2 hatchback 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 F40 — it is a tool-led job, with a manual fallback if you have no scanner.

What service mode is and why the F40 needs it

Each rear caliper carries a geared motor that drives the parking-brake piston. With the system 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 F40

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. On the F40 (including the M135i) BimmerLink’s service / workshop mode works well; BMW ISTA, Foxwell or a Schwaben/Autel EPB tool work too. Open the parking-brake service function and run service / install position. You’ll hear the rear motors whir as the pistons retract.
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 F40’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 writes off an expensive 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. Pump the pedal until firm before moving the car. While the tool is connected, reset the rear-brake CBS (Condition Based Service) counter in BimmerLink or ISTA 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

Does BimmerLink work on the F40? Yes — the F40 (M135i confirmed) is a BMW where BimmerLink’s service / workshop mode reliably retracts the rear pistons, so you don’t necessarily need full ISTA.

Can I do it with no tool at all? Yes, by the manual route — release the EPB, unbolt each rear actuator and wind the spindle in clockwise. You’ll still want a tool afterwards to reset the rear-brake CBS reminder cleanly.

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 F40 on a charger and retry; the EPB motors need a strong 12 V supply.

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