Pixhawk arm motor speed not same

hello i need same help when arm motor 1 / 2/ 3 spin when my throttle at 0 level and motor 4 no spin, when i move the throtle a bit up from 0 point of my throtle than the motor 4 spin,… I switch the motor 1 and esc 1 to motor 4 still same problem motor 4 and esc 4 works well at 1…so this shows there is no problem with my motor and esc …is the any setting at pixhawk 4 that i can change …tq