To repair BMW dynamic ESA shock absorbers, you need to refill oil in the damper, and therefore open the dynamic valve to properly fill and vacuumize the shock absorber. This special tool lets you open the dynamic valve of the shock absorber. When you are unable to open the valve, the valve housing isn’t filled with oil. The function of dynamic ESA will be reduced a lot.
You can also use the device to test if the dynamic valve works on the bike, or if it is broken. Simply by disconnecting the demping connector, which is hidden underneath the saddle/ computer, and the valve tester connects the device. When you press valve open, and you push firmly on the rear end of the bike, the bike starts bouncing back/ zero damping. When you close the valve, and press firmly again, the bikes feels harsh.