Circuit/System Description

The reductant injector is a component of the selective catalytic reduction system used to dose the reductant fluid to the exhaust gas and participate in the reduction reactions. The Engine Control Module (ECM) calculates the injection time of the reductant injector based on the measurement of the NOx sensors. To activate the injector the ECM supplies a Pulse Width Modulated signal to the high control circuit and the low control circuit is always commanded ON. The reductant injector temperature is modeled based on internal injector resistance of the injector coil and is used to monitor the temperature of the injector to prevent damage.