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 (PCM) controls the closed loop which then controls the fuel injection volume. While the above controls is going on and if WUTWC 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 (PCM) 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, P0430
Refer to DTC P0420 / P0430: Catalyst System (Bank-1 / -2) Efficiency below Threshold:H25 Engine.
Operation:
Enable Conditions:
Typical Malfunction Thresholds:
Catalyst Monitor
Mode $06 Data:
MODE $06 Data