Circuit/System Description

The diesel oxidation catalyst, main function is to control emissions of non methane hydrocarbons and soluble organic fraction. Its secondary function is to assist with the diesel particulate filter (DPF) regeneration, by obtaining and sustaining the temperature necessary for regeneration. In order to generate the high exhaust temperatures needed for regeneration, the aftertreatment system increases exhaust temperatures by injecting diesel fuel directly into the exhaust gases entering the DOC. This is accomplished by means of an ECM-controlled fuel injector called the hydrocarbon injector (HCI), also referred to as the indirect fuel injector or exhaust aftertreatment fuel injector. The fuel injector is located in the exhaust pipe upstream of the DOC. The injected fuel is converted into heat by the DOC to incinerate soot accumulated in the DPF. The engine control module (ECM) monitors the exhaust gas temperature sensor 1 and 2 to determine if the operating temperature of the catalyst is achieved during a regeneration event.

The hydrocarbon conversion to oxygen is calculated from the heat flow in the oxidation catalyst, based on measured and modeled temperatures, to determine the efficiency of the oxidation catalyst. The modeled temperatures are calculated using the injection quantity and air mass flow. When the ECM detects that the diesel oxidation catalyst hydrocarbon conversion rate is below a calibrated threshold during an active regeneration event this DTC sets.