LEMON Manuals: Even more car manuals for everyone
Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 362 (Engine Controls Self-Diagnostics) >> Diagnostic Tests >> DTC P0420: TWC System - Low Efficiency >> Conditions For Running DTC

Conditions For Running DTC

WARNING: This page is about a different car, the 2003 Pontiac Aztek and 2003 Buick Rendezvous. However, it is still accessible from the selected car via links, so may be relevant.
  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.