Circuit/System Description

The secondary air injection system aids in the reduction of hydrocarbon emissions during a cold start. The electric air pump forces fresh air into the exhaust stream in order to accelerate the catalyst operation. A pressure sensor for secondary air injection is used to monitor air flow from the secondary air injection pump. The ECM sends a voltage to the 5 V reference circuit and earth to the low reference circuit. The sensor provides a signal voltage to the ECM relative to the pressure changes within the secondary air injection system.

Ignition voltage is supplied directly to the secondary air injection pump relay. The ECM controls the relay by grounding the control circuit, which activates the secondary air injection pump relay. With the relay contacts closed, battery voltage is supplied to the secondary air injection pump.