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Home >> Buick >> 2008 >> Allure CX >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System & Fuel System - 3.8L - DTC P0385 To DTC P2108 >> DTC P0420 >> Repair Verification
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Repair Verification

  1. Clear the DTCs.
  2. Allow the engine coolant temperature to reach 70°C (156°F).
    • Place the gear selector in Park for the automatic transmission, or Neutral for the manual transmission.
    • Set the parking brake.
  3. Press and hold the service brake.
  4. Run the engine for 6 minutes at 2500 RPM.
  5. Allow engine speed to return to idle speed, then place gear selector into Drive for the automatic transmission, or apply clutch pedal for the manual transmission.
  6. After 2 minutes, verify that DTC P0420 has passed or failed this ignition cycle.
    • If not passed or failed this ignition cycle, the test aborted resulting in an inconclusive test result. The above test may need to be repeated up to 5 more times during this drive cycle. The first test should be run after the initial warm up period of 6 minutes. Between subsequent tests maintain 2,500 RPM for 2 minutes.
  7. If 6 tests have been attempted and the DTC has not run or passed during this key cycle, turn the key to OFF for 30 seconds, then run the procedure a second time.
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