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Home >> Suzuki >> 2002 >> XL-7 Plus >> Repair and Diagnosis >> External Pages >> Different car >> Section 14 (Engine Controls - Self-Diagnostics - 1.6L) >> Diagnostic Tests >> DTC P0420: Catalyst System Efficiency Below Threshold >> Diagnosis & Repair Procedure
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Diagnosis & Repair Procedure

WARNING: This page is about a different car, the 2002 Suzuki Esteem. However, it is still accessible from the selected car via links, so may be relevant.
  1. If engine system check has been performed, go to next step. If engine system check has not been performed, go to A4: ENGINE SYSTEM CHECK  under SYSTEM TESTS.
  2. If short term fuel trim was 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 OR P0172  .
  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 TWC. After repair, repeat 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 Blue wire between HO2S No. 2 and ECM. See WIRING DIAGRAMS article. Also, check for open or short in Pink wire between HO2S No. 2 and ECM. If no problem is found, replace HO2S No. 2. If problem is found, repair as necessary. After repair, repeat DTC CONFIRMATION TEST  .
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