Dtc P0420 Catalyst System (Bank-1) Efficiency Below Threshold Dtc P0430 Catalyst System (Bank-2) Efficiency Below Threshold - Suzuki Engine 2002 GRAND VITARA SQ420 Service Manual

DTC P0420 Catalyst System (Bank-1) Efficiency Below Threshold
DTC P0430 Catalyst System (Bank-2) Efficiency Below Threshold
SYSTEM / WIRING DIAGRAM
[A] : Terminal arrangement of ECM (PCM) coupler viewed from harness side
1. Warm up TWC converter (Bank 2)
2. Warm up TWC converter (Bank 1)
SYSTEM DESCRIPTION
Exhaust oxygen concentration at the upper part and the lower part of TWC is detected from HO2S-1 and HO2S-
2 respectively and accordingly ECM (PCM) controls the closed loop which then controls the fuel injection vol-
ume. While the above control is going on and if TWC is in good condition, the output voltage of HO2S-2 is main-
tained at specified level. As TWC is in becomes deteriorated, even when the above control is going on, the
exhaust gas which has passed TWC then passes HO2S-2 at the exhaust oxygen concentration similar to that of
the upper part of TWC without being oxygenated or converted. Thus, waveforms of HO2S-1 and HO2S-2 output
voltage become alike. ECM (PCM) judges deterioration of TWC by comparing waveforms of HO2S-1 and
HO2S-2.
ENGINE GENERAL INFORMATION AND DIAGNOSIS (H25 ENGINE) 6-1-113
3. TWC converter
4. HO2S (Bank 2, Sensor 2)
5. HO2S (Bank 2, Sensor 1)
6. HO2S (Bank 1, Sensor 1) 9. Bank 2
7. HO2S (Bank 1, Sensor 2)
8. Bank 1