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Home › Saturn › 2006 › Relay 3.9 1, AWD › Repair and Diagnosis › Engine Performance › System › Engine Controls - 3.9L - DTC P0010 To DTC P0420 › DTC P0420 › Circuit/System Testing

Circuit/System Testing

NOTE: Refer to Heated Oxygen Sensor Resistance Learn Reset Notice .
NOTE: Refer to Three-Way Catalytic Converter Damage Notice .
    IMPORTANT: A new catalyst may fail this test due to out-gassing of the internal matting. If this occurs, operate the vehicle at highway speeds for approximately one hour and retest.
  1. Inspect the catalytic converter for the following conditions:
    • Dents
    • A severe discoloration caused by excessive temperatures
    • Road damage
    • An internal rattle caused by damaged catalyst substrate
    • Restrictions
    • If a condition is found, then replace the catalytic converter.
  2. Inspect the exhaust system for the following conditions:
    • Leaks
    • Physical damage
    • Loose or missing hardware
    • If a condition is found, then replace the exhaust system or components, as necessary.
  3. Inspect the HO2S 2 sensor for proper torque.
    • If the HO2S 2 sensor does not have proper torque, correctly torque the sensor.
  4. Inspect the HO2S 2 sensor and circuits for the following conditions:
    • Grounded or chafing wiring harness
    • Damage
      • If a condition is found, then replace the HO2S 2.
      • If no physical condition is detected, perform the following:
    • Clear all DTCs.
    • Operate the vehicle under the Conditions for Running the DTC.
      • If DTC P0420 runs and fails, replace the converter.
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