An air injection system is applied to some four-cylinder engines to help catalytic converters warm up and reach their optimal working temperature during the warm-up modes. PCM, electric air pump, air injection control valve, air pressure sensor, air injection control driver make up this system. The PCM draws information from the CKP sensor, ECT sensor, and MAF/IAT sensor to know the temperature of the engine. If the engine is cold the PCM is determining the amount of air that is needed to warm up the catalysts, the air injection system is activated for a maximum at 80 seconds. The air injection control driver involved turns on the electric air pump and control valve which injects air into the exhaust ports, helping in burning the unburned fuel fumes commonly experienced during warm-ups. It also increases the rate at which exhaust gases and the earlier located catalysts in the pipe are heated. However, most of the components of the air injection system are very reliable; nonetheless, the air pressure sensor, electric air switching valve, the air pump can be replaced if they fail-which in certain situations may necessitate removal of Intake manifold. Air pump assembly is mounted in the right-front corner of the engine compartment while the air switching valve assembly is mounted at the top of the exhaust manifold. It is situated on the back part of intake air connector as the air pressure sensor. These components include electrical connectors and hoses, together with the mounting bolts used in their removal and installation processes, where the sequence is to disconnect and later reconnect but ensure that when connecting, new gasket is used where required.