A system for inflating and deflating pneumatic tires of a vehicle through pneumatically actuated tire isolating valves which isolate air under pressure in the tires from the system comprises electronically controlled valves for achieving opening of the tire isolating valves, inflating or deflating of the vehicle tires and the quick exhausting of air under pressure from the system when the desired tire pressure is reached so as to immediately enable closure of the tire isolating valves to assure obtaining the desired pressure in the tires. Optimum rates of inflating and deflating together with accuracy in obtaining a desired tire pressure are achieved through a unique tire isolating valve construction and electronic controlled circuitry by which signals corresponding to desired and existing tire pressures are electronically compared to provide output signals by which the inflating, deflating and exhaust functions are controlled.