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Home >> Suzuki >> 2003 >> XL-7 Limited, 4WD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Monitors >> Catalyst Monitor >> System Description
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System Description

Exhaust oxygen concentration at the upper part and the lower part of Warm Up-Three Way Catalyst (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 control 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.

The system has 4 oxygen sensors located upstream and downstream of the catalysts. The layout of catalysts and oxygen sensors is indicated in illustration. See Fig 1.

Fig 1: Catalyst System Layout
G00253065Courtesy of SUZUKI OF AMERICA CORP.
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