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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 77 (Engine Controls Self-Diagnostics - 5.0L & 5,7L) >> Diagnostic Tests >> DTC P0420 & P0430: TWC System - Low Efficiency - Bank 1 & 2 >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2002 GMC Savana Special, 2002 GMC Savana Camper Special, 2002 GMC Savana, 2002 Chevrolet RV Cutaway, and 2002 Chevrolet Cutaway. However, it is still accessible from the selected car via links, so may be relevant.
  1. Did you perform the Diagnostic System Check-Engine Controls? If yes, go to next step. If no, see DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM.
  2. Are any other DTCs set? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, go to next step.
  3. Check the exhaust system for leaks and loose or missing hardware. Repair conditions, as necessary. Did you find and correct the condition? If yes, go to step  5. If no, go to next step.
  4. Verify that the correct original equipment three-way catalytic converter is installed. Check the converter for the following:
    • Dents
    • Severe discoloration
    • Holes
    Ensure that the oxygen sensors are properly installed and that the wiring connections are properly retained and not damaged. Did you find a problem? If yes, go to next step. If no, go to step  6.
  5. Using the scan tool, clear the DTCs. Start the engine. Allow the engine to idle until the engine reaches normal operating temperature. Select DTC and the Specific DTC function. Enter the DTC number that was set. Operate the vehicle, within the Conditions for Setting this DTC, until the scan tool indicates the diagnostic Ran. Does the scan tool indicate the diagnostic Passed? If yes, system is okay. If no, go to step  2.
  6. Replace the catalytic converter. After repairs, system is okay.