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Home >> Suzuki >> 2001 >> Swift GA, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0420: Catalyst System Efficiency Below Threshold >> Diagnosis & Repair Procedure

Diagnosis & Repair Procedure

  1. Perform DTC CONFIRMATION TEST . If DTC P0420 is set, go to next step. If DTC P0420 is not set, problem is intermittent. System is okay at this time. See TROUBLE SHOOTING - NO CODES article.
  2. If short term fuel trim is between -20 and +20 percent when DTC CONFIRMATION TEST was performed, go to next step. If short term fuel trim was not as specified, check fuel system operation. See DTC P0171: TOTAL FUEL TRIM IS GREATER THAN ALLOWED SPECIFICATION, OR P0172: TOTAL FUEL TRIM IS LESS THAN ALLOWED SPECIFICATION .
  3. Using scan tool, perform following while observing HO2S No. 2 readings. Ensure fuel tank is at least 1/4 full, vehicle is at an altitude of 8000 feet or below, barometric pressure is 75 kPa or more, ambient temperature is 14°F (-10°C) or more, and intake air temperature is 158°F (70°C) or less. Ensure no exhaust leaks are present. Start engine and allow it to reach normal operating temperature. Drive vehicle for 5 minutes. Record HO2S No. 2 output voltage and short term fuel trim, while driving, using DATA LIST mode on scan tool. Stop vehicle. Drive vehicle at speeds of more than 20 MPH and stop vehicle, 4 times. Go to next step.
  4. Drive vehicle at speed of about 50 MPH in 3rd gear (M/T) or 2nd gear (A/T). Release accelerator pedal and allow vehicle to coast for 10 seconds or more. Stop vehicle and allow engine to idle for 2 minute. If HO2S No. 2 scan tool readings are more than 0.6 volts and less than 0.3 volts, replace catalytic converter and go to DTC CONFIRMATION TEST . If HO2S No. 2 scan tool reading are not as specified, go to next step.
  5. Check for open or short in Light Green/Black wire between HO2S No. 2 terminal No. 1 and PCM 22-pin connector C23 terminal No. 22, and in Yellow wire between HO2S No. 2 terminal No. 2 and PCM 22-pin connector C23 terminal No. 10. See Figure. If wires are okay, replace HO2S No. 2 and go to DTC CONFIRMATION TEST .
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