Check the tire pressure at a few positions and see if the pressure is over the target pressure listed on the controller. The pressure relief module is designed to let air out of the tires is pressure is 10 psi over target. If you tire pressure is high, the PRM is doing it's job. But if tire pressure is normal I would suspect the PRM itself is bad, or the inflation/deflations pressures are set incorrectly, causing the system to constantly add, then relieve air pressure.