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Home >> Chevrolet >> 2003 >> Venture Base, Van Cargo Extended >> 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, 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.
    • Engine is in Closed Loop.
    • Intake Air Temperature (IAT) is -4 to 212°F (-20 to 100°C).
    • Battery voltage more than 10.7 volts.
  2. Warm up the catalyst.
    • Fully open the hood.
    • Transaxle is in Park (A/T) or Neutral (M/T).
    • Set parking brake.
    • Press and hold 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 1 minute.
    • In order to activate the diagnostic, return the engine to idle and place transaxle Drive (A/T) or depress the clutch pedal (M/T).
  3. Test the catalyst.
    • The transaxle is in Drive (A/T) or Neutral (M/T) with clutch pedal depressed.
    • Within 60 seconds the air/fuel ratio will go lean (less than 14.1:1 for up to 7 seconds). The air/fuel ratio may then go rich (more than 15.3:1 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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