Description: Air injection technology first appeared during the late 1960s and was used extensively throughout the 1970s. It was still widely used by some manufacturers through the 1980s, but applications began to fade as automakers developed cleaner-running engines. The typical mechanical air injection system consists of a network of hoses and tubes, a belt-driven air pump and air-management valves. Since that time, air injection systems have become more diverse in nature, sometimes using the onboard computer to control system operation. Some engines use pulse-air systems that do not use a pump. Instead, alternating pressures in the exhaust stream are used to pull air into the exhaust system. As obsolete as this technology seems, some late-model vehicles use a high-tech air injection system using an electric air pump controlled by the vehicle's Powertrain Control Module (PCM).