GMC 12568324 Pump Assembly, Secondary Air Injection

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Certain engines, such as the 4.3L V6, 5.7L V8, and 7.4L V8 engines, are equipped with a Secondary Air Injection (AIR) system. The purpose of this system is to reduce the levels of unburned hydrocarbons (HC) and carbon monoxide (CO) in the exhaust gases by introducing fresh air into hot exhaust gases flowing through the exhaust manifolds. The AIR pump, vacuum control solenoid, check valves, shut-off valve, and hoses and pipes are some of its components. The AIR pump sucks filtered outside air and pushes it into the exhaust manifolds under the control of the PCM. The AIR shut-off valve is controlled by the vacuum control solenoid to open up and allow air from the pump to pass through to get to check valves. These check valves block backflow of exhaust gases inside the AIR system. Some signals that activate it include coolant temperature or engine deceleration when determined by PCM. If certain conditions are met, PCM can deactivate its electric clutch for AIR pump. If simple checks do not solve a problem, then checked or replaced should be done only at a qualified repair shop's.