The Air Injection Pump in the Engine



Speaking of the sophisticated make-up of a vehicle’s engine, somewhere in there is a well-engineered vacuum system comprising of the vacuum switching valve (VSV), the air pump and a network of valves and air passages.

Along the engine, passage ways are the secondary air injection. A manual start-up of the pump should give an average change of the voltage in the oxygen sensors. Should the air pump fail in its task of heating up the triple-fold catalyst, for the upgraded vehicle engines, the engine management is tasked to know that through the Digital Motor Electronics (DME). The DME is programmed to self-test the air pump through an attached computer. Therefore, each time the car is started, the DME is tuned to turn the air pump on at some point in the cycle and see if it is working. The mechanism of operation of the DME is quite interesting as you will see. In newer car models, oxygen sensors have been incorporated into part of the fuel management system. Broadband oxygen sensors are also an alternative for the same. These sensors detect the oxygen levels in the exhaust gases and then report back to the DME, which makes the necessary tweaks in the mixture of air and fuel going to the engine to enhance the most effective performance under any given conditions. Know more about cars at

The oxygen sensors also inform the DME if the air is the reaching to the catalyst from the air pump. In the proper working conditions of the secondary air injection, the DME should be able to detect a voltage drop in a standard oxygen sensor. For the newer air/fuel sensors, your car technician will need the fuel trim data to check whether the fuel system is making a point of adjusting when the air pump is triggered artificially. In addition to the mechanism of the air pump pushing air, some mechanical controls also aid in getting air to the exhaust side. These include the vacuum switch valve (VSV) and the vacuum controlled “Dump Valve.” When vacuum is applied through the VSV, air is allowed to enter into the exhaust via a check valve which prevents exhaust fumes from returning through the “Dump Valve,” which might damage it as well as the pump.

This entire mechanism summarizes that the DME activates the air pump. If the sensors detect no change, they highlight a secondary air injection malfunction or a low flow, then DME activates the Check Engine Light, and a diagnostic trouble code is generated and kept in the engine’s management processor or the DME.


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