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Home >> Chevrolet >> 2001 >> Venture Base, Van Passenger >> Repair and Diagnosis >> External Pages >> Different car >> Section 158 (Engine Controls Self-Diagnostics - 2.2L) >> Diagnostic Tests >> DTC P0420: TWC System - Low Efficiency >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different car, the 2003 Pontiac Sunfire, 2003 Pontiac Grand Am, 2003 Oldsmobile Alero, and 2003 Chevrolet Cavalier. However, it is still accessible from the selected car via links, so may be relevant.
  1. Perform diagnostic system check - engine controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
  2. Turn ignition switch to RUN position, engine off. Install scan tool. Were any component DTCs are set? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, go to next step.
  3. Turn ignition switch to OFF position. Check the following conditions:
    • Inspect the exhaust system for leaks.
    • Inspect the rear Heated Oxygen Sensor (HO2S) 2 for leaks.
    Did you find a condition? If yes, go to next step. If no, go to step  5.
  4. Repair exhaust system as necessary. After repair, go to step  6.
  5. Replace TWC converter. After repair, go to next step.
  6. Using scan tool, clear DTCs. Turn ignition switch to OFF position for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See CONDITIONS FOR RUNNING DTC . Did the DTC fail this ignition? If yes, go to step  2. If no, go to next step.
  7. Using a scan tool, observe the CAPTURE INFO. Does the scan tool display any DTCs that you have not diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay at this time.
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