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Home › Pontiac › 2006 › G6 Base, 2.4 B › Repair and Diagnosis › Engine Performance › System › Engine Control System - 2.4L - DTC P0351 To DTC P2138 › DTC P0420 › Circuit/System Testing

Circuit/System Testing

NOTE: Refer to Three-Way Catalytic Converter Damage Notice .
NOTE: Refer to Heated Oxygen Sensor (HO2S) Resistance Learn Reset Notice .
IMPORTANT: A new converter with less than 100 miles on it may set P0420 due to out-gassing of the internal matting. Operating the vehicle at highway speeds for approximately 1 hour may correct the condition.
  1. With the engine in closed loop and at operating temperature, increase the engine speed to 1,500 RPM for one minute and then return to stabilized idle. Observe that the HO2S 2 voltage parameter is not as active as the HO2S 1 voltage parameter.
    • If it is as active then proceed with Circuit/System Verification.
  2. 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, replace the catalytic converter.
  3. Inspect the exhaust system for the following conditions:
    • Leaks
    • Physical damage
    • Loose or missing hardware
    • Properly torqued HO2S
    • If a condition is found, repair the exhaust system.
  4. Inspect the HO2S 2 for the following conditions:
    • A grounded wiring harness
    • Damage
    • If a condition is found, replace the HO2S 2.
    • 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 one minute and then returning to a stabilized idle, replace the catalytic converter.
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