Just replaced the rear pads on my 2016 and the rear wheels turn freely but as soon as I start the car, I hear a buzzing noise and the rear wheels lock up. As soon as I turn the power off, the wheels turn freely. Start the car again and within a couple of seconds, the rear wheels lock up again. It not a total lockup, but I can’t turn it by hand, I need a bar to turn it. just a quick trip down the road turned the new rotor blue. I did make sure the slot in the caliper piston slot was aligned properly, brake pads move smoothly in the guides and caliper moves freely on the pins.
The buzzing noise in the front is a small pump that builds up brake fluid pressure, but the pressure is only to be stored in an accumulator until the brake system opens valves to apply the pressure to the brakes. If the pumping-up of accumulator pressure is being accompanied immediately by pressure at rear brakes, without any use of the pedal, I would suspect some valve(s) in the actuator not closing tightly.
