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 is used to monitor the air pressure from the secondary air injection pump. The Engine Control Module (ECM) supplies voltage to the 5 V reference circuit and provides a ground for the low reference circuit. The sensor provides a signal voltage to the ECM relative to the pressure changes within the secondary air system.

Ignition voltage is supplied directly to both the secondary air injection pump relay and the secondary air injection valve relay coils. The ECM activates the secondary air system by simultaneously supplying a ground reference to the secondary air injection pump and valve relay coils. This energizes the relays and allows battery (B+) voltage to be connected to the pump and the control valve/pressure sensor assembly through the relay contacts. The pump motor energizes and the control valve opens allowing air flow into the exhaust manifold.