What do you mean your power module is not working? Are you getting weird readings for voltage and current or no readings at all? Have you gone through to calibrate your power module? Details on how to calibrate your power moude can be seen here.
Otherwise where did you get yor pixhack kit from, as I know some Chinese sellers try save costs by only including the BEC on the power module so it does not have the capability to measure current or voltage, but only provides a constant 5V to power your pixhawk.