Although the emissions control systems for both fuel injected and turbocharged engines perform the same function, they require different checks and servicing. Due to the link between these systems to the fuel, exhaust and engine electrical systems, they must be checked while handling emissions-related issues. The air control valve and reed valve make up the air injection system, which pulls air into the exhaust manifold, to lower hydrocarbon emissions. The process of checking includes testing of idle airflow at idle and higher RPMs and checking the operation of the air control and reed valves, which may need to be replaced. The charcoal canister absorbs fuel vapors from the evaporative emissions control system to utilize for engine operation. The vacuum level in several locations and the correct operation of valves are checked as part of its functionality. The PCV valve can be removed from any warm Idle engine to confirm the operation of the positive crankcase ventilation system. This will be evidenced by a change in engine Idle speed. The exhaust gas recirculation (EGR) system routes exhaust gas into the intake manifold to reduce NOx emissions. Most EGR checks will focus on the vacuum hose and valve. All of the components of these systems can be carefully disconnected and reassembled after ensuring every fixture and itself has perfect sealing.