Catalyst Monitor
OBD System Description - Catalyst MonitorSystem Description / Monitoring Procedure
Exhaust oxygen concentration at the upper part and the lower part of WU-TWC is detected from HO2S-1 and HO2S-2 respectively and accordingly ECM controls the closed loop which then controls the fuel injection volume. While the above controls is going on and if WU-TWC is in good condition, the output voltage of HO2S-2 is maintained at specified level. As WU-TWC becomes deteriorated, even when the above control is going on, the exhaust gas which has passed WU-TWC then passes HO2S-2 at the exhaust oxygen concentration similar to that of the upper part of WU-TWC without being oxygenated or converted. Thus, waveforms of HO2S-1 and HO2S-2 output voltage become alike, ECM judges deterioration of WU-TWC by comparing waveforms of HO2S-1 and HO2S-2.
Catalyst System Layout
The system has 4 oxygen sensors located upstream and downstream of the catalysts. The layout of catalysts and oxygen sensors is described.
Catalyst and HO2S layout
DTC Description / Detecting Condition / Confirmation Procedure
P0420
Refer to DTC P0420: Catalyst System Efficiency below Threshold (Bank 1):H27 Engine.
P0430
Refer to DTC P0430: Catalyst System Efficiency below Threshold (Bank 2):H27 Engine.
Operation:
Enable Conditions:
Common Prohibition Mode:
Typical Malfunction Thresholds:
Catalyst Monitor
Mode $06 Data:
MODE $06 Data