System Description/Monitoring Procedure

WARNING: This page is about a different car, the 2006 Suzuki Grand Vitara. However, it is still accessible from the selected car via links, so may be relevant.

Exhaust oxygen concentration at the upper part and the lower part of WU-TWC is detected from A/F sensor and HO2S 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 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 at the exhaust oxygen concentration similar to that of the upper part of WU-TWC without being oxygenated or converted. Thus, waveforms of A/F sensor and HO2S output voltage become alike, ECM judges deterioration of WU-TWC by comparing waveforms of A/F sensor and HO2S.