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Home >> Buick >> 2008 >> Allure CXS >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System & Fuel System - 3.6L - DTC P0335 To DTC P2097 >> DTC P0420 >> Circuit/System Testing
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Circuit/System Testing

  1. Observe the scan tool DTC information. Verify there are no HO2S, or misfire DTCs set.
  2. Inspect and verify the following:
    • The catalytic converter is an original part
    • The HO2S 2 is secure and the wiring is not damaged, or contacting the exhaust
    • The exhaust system for leaks, damage, or missing hardware
    • If a condition is found, repair as necessary.
  3. IMPORTANT: Before replacing the catalytic converter, correct any conditions that may have damaged the converter.
  4. If a condition is not located, replace the catalytic converter.