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Home >> Pontiac >> 2003 >> Aztek AWD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls Self-Diagnostics >> Diagnostic Tests >> DTC P0420: TWC System - Low Efficiency >> Conditions For Running DTC
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Conditions For Running DTC

  1. Meet the conditions for engine warm-up. Use the scan tool catalyst data list in order to verify the following conditions:
    • DTCs P0030, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0128, P0130, P0131, P0132, P0133, P0134, P0135, P0137, P0138, P0140, P0141, P0171, P0172, P0201-P0206, P0300, P0336, P0341, P0404, P0405, P0410, P0440, P0442, P0443, P0502, P0503, P0506, P0507, P1133, P1134, P1351, P1352, P1361, P1362, or P1441 not set.
    • Engine has been running longer than 10 minutes.
    • Engine Coolant Temperature (ECT) is 169-255°F (76-124°C).
    • Barometric (BARO) pressure is above 75 kPa.
    • Vehicle is in Closed Loop.
    • Intake Air Temperature (IAT) is -4 to 212°F (-20 to 100°C).
    • Battery voltage greater than 10.7 volts.
  2. Warm up the catalyst.
    • Fully open the hood.
    • Transmission in Park (A/T) or Neutral (M/T).
    • Set parking brake.
    • Press and hold the service brake.
    • Each time the engine is started the diagnostic can run up to 18 times. After the 10-minute run time, and before the diagnostic runs the first time, the engine must run an additional 5 minutes between 1500-2500 RPM. For any additional tests on the same key cycle, the engine must be between 1500-2500 RPM for one minute.
    • In order to activate the diagnostic, return the engine to idle and place transaxle in Drive (A/T) or depress clutch pedal (M/T).
  3. Test the catalyst.
    • The transaxle is in Drive (A/T) or Neutral (M/T) with the clutch pedal depressed.
    • Within 60 seconds the air/fuel ratio will go lean, less than 14.1, for up to 7 seconds. The air/fuel ratio may then go rich, greater than 15.3, for up to 7 seconds.
    • Using scan tool, check and see if DTC P0420 has passed or failed this key cycle.
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