Secondary Air Injection The ECM controls the secondary air injection which is used to quickly heat the catalytic converters for emission legislation compliance. 1 Non return valve 2 Vacuum vent valve 3 Vacuum reservoir 4 SAI pump The ECM controls the vacuum vent valve and the air injection pump relay. The air pump operates at a start temperature of between C and C. The pump continues to operate fora maximum of 2 minutes, when the engine speed drops to idle. Note that the secondary air valve is always open when the air pump is operating. The secondary air injection system is used to limit the emission of carbon monoxide (CO) and hydrocarbons (HC) that are prevalent in the exhaust during cold starting of a spark ignition engine. The concentration of hydrocarbons experienced during cold starting at low temperatures are particularly high until the engine and catalytic converter reach normal operating temperature. The lower the cold start temperature, the greater the prevalence of hydrocarbons emitted from the engine.