System Description
The emission control system includes the Warm-up Three way Catalytic Converter (WU-TWC), Three Way Catalytic Converter (TWC), Exhaust Gas Recirculation (EGR) system and Positive Crankcase Ventilation (PCV) system. The emission control system is designed to meet federal and state emission standards.
Description
The Warm-up Three way Catalytic Converter (WU-TWC) and Three Way Catalytic Converter (TWC) are used to convert hydrocarbons (HC), carbon monoxide (CO), and oxides of nitrogen (NOx) in the exhaust gas to carbon dioxide (CO 2 ), dinitrogen (N 2 ) and water vapor.
Scheme 108
Scheme 109
This system evaluates the catalyst's capacity by means of the HO2S (Primary and Secondary) output during stable driving conditions. If deterioration has been detected during two consecutive driving cycles, the MIL comes on and DTC P0420 will be stored.
Note. If some of the DTCs listed below are stored at the same time as DTC P0420, troubleshoot those DTCs first, then troubleshoot DTC P0420.
P0137, P0138: Secondary HO2S (Sensor 2)
P0141: Secondary HO2S (Sensor 2) Heater
Note. For diagnosis of P0137, P0138 and P0141, see PGM-FI SYSTEM (GX) .
The EGR system reduces oxides of nitrogen (NOx) emissions by recirculating exhaust gas through the EGR valve and the intake manifold into the combustion chambers. The PCM memory includes the ideal EGR valve lift for varying operating conditions.
The EGR valve lift sensor detects the amount of EGR valve lift and sends it to the PCM. The PCM then compares it with the ideal lift in its memory (based on signals sent from other sensors). If there is any difference between the two, the PCM cuts current to the EGR valve.
Scheme 110
Deterioration (clogging, leakage, etc.) in the EGR line or EGR valve is detected by means of the changes in MAP before and after the operation of the EGR valve.
If deterioration has been detected during two consecutive driving cycles, the MIL will come on and DTC P0401 will be stored.