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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 83 (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 2002 GMC Sonoma and 2002 Chevrolet S10 Pickup. 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, go to next step.
  2. Are any other DTCs set? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, go to next step.
  3. Verify that TWC is an original equipment part. Check TWC for damage such as dents, severe discoloration caused by excessive temperature, holes, rattle caused by damaged catalyst, etc. Check exhaust system for leaks, damage, or loose or missing hardware. Ensure that O2S 1 and HO2S 2 are secure and that pigtails and wiring are not damaged or contacting exhaust. Did you find and correct the condition? If yes, go to step  5. If no, go to next step.
    NOTE: Before replacing a TWC, correct any condition that may have damaged the TWC.
  4. Replace catalytic converter. After repairs, go to next step.
  5. Use the scan tool in order to clear the DTCs. Turn ignition off for 30 seconds. Start engine. Operate the vehicle within the Conditions for Running the DTC. See CONDITIONS FOR RUNNING DTC . Does the DTC run and pass? If yes, go to next step. If no, go to step  2.
  6. With a scan tool, observe the stored information, 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.
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