See Figures 1
The secondary air supply system is used on feedback carburetor engines only. It consists of a reed valve, a secondary air control valve, a secondary air control solenoid valve, an ECU and a sensor.
The reed valve supplies secondary air into the exhaust manifold for the purpose of promoting oxidation of exhaust emissions during the engine warm-up, deceleration and hot start operation. The reed valve is actuated by exhaust from pulsations in the exhaust manifold. Additional air is supplied into the exhaust manifold through the secondary air control valve.
The secondary air control valve is opened by the intake manifold vacuum when the solenoid valve is energized by the ECU, based on information on coolant temperature, engine speed, time and idle position.