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Home >> Chevrolet >> 2006 >> Optra LS, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - 1.4L DOHC >> Diagnostic Information and Procedures >> DTC P0420 >> Circuit/System Testing
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Circuit/System Testing

  1. Verify there are no HO2S or misfire DTCs set.
    • If there is an HO2S or misfire DTCs are set, refer to Diagnostic System Check - Vehicle to diagnosis the applicable DTC, before proceeding with this diagnostic procedure.
  2. Verify the following conditions do not exist with the catalytic converter:
    • Dents
    • A severe discoloration caused by excessive temperatures
    • Road damage
    • An internal rattle caused by damaged catalyst substrate
    • Restrictions
    • If a condition is found, replace the catalytic converter.
  3. Verify the following conditions do not exist with the exhaust system:
    • Leaks
    • Physical damage
    • Loose or missing hardware
    • Properly torqued HO2S
    • If a condition is found, repair the exhaust system.
  4. Verify the following conditions do not exist with the HO2S 2:
    • A grounded wiring harness
    • Damage
    • If a condition is found, replace the HO2S 2.
  5. If no physical condition is detected and the HO2S 2 is as active as the HO2S 1 after operating the engine at 1,500 RPM for 1 minute and then returning to a stabilized idle, then replace the catalytic converter.
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