Circuit/System Description

The diesel oxidation catalyst (DOC), main function is to control emissions of non methane hydrocarbons and particulate (soot). 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 after treatment system increases exhaust temperatures by injecting diesel fuel into the exhaust system via post-injection. 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 cold-start catalyst warm-up.

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 a cold-start catalyst warm-up phase, this DTC sets.