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Home › Chevrolet › 2001 › Metro › Repair and Diagnosis › Engine Performance › System › Engine Controls Self-Diagnostics - 1.3L › Diagnostic Tests › DTC P0420: Catalyst System Low Efficiency › Diagnostic Procedures

Diagnostic Procedures

  1. Perform powertrain diagnostic system check. See POWERTRAIN DIAGNOSTIC SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
  2. Check for HO2S DTCs and diagnose those DTCs first. If DTC P0131, P0132, P0133, P0134, P0135, P0136, or P0141 is set, diagnose affected DTCs. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no other DTC is set, go to next step.
  3. Start and warm engine to normal operating temperature. Ensure engine is operating in closed loop. Run engine at 2500-3000 RPM for 3 minutes. Using scan tool, monitor HO2S-1 and HO2S-2 signals. If HO2S-1 signal is as active as HO2S-2 signal, go to step  5. If HO2S-1 signal is not as active as HO2S-2 signal, go to next step.
  4. Turn ignition on, with engine off. Using scan tool, clear DTC information. Using scan tool, place vehicle into check mode. Operate vehicle within FREEZE FRAME/FAILURE RECORDS data conditions. If DTC P0420 resets, go to next step. If DTC P0420 does not reset, check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
  5. Check TWC for severe discoloration caused by excessive temperatures. Check for dents, holes or an internal rattle, indicating damaged catalyst. Ensure TWC meets manufacturer's specification. If any problems are found, go to step  8. If no problems are found, go to next step.
  6. Check exhaust system for loose or missing hardware, leaks, or damage. Repair as necessary. After repairs, go to step  9. If exhaust system is okay, go to next step.
  7. Check HO2S-2 for proper installation and for road damage. Ensure HO2S-2 wire harness is not contacting exhaust system. Repair as necessary. After repairs, go to step  9. If HO2S-2 is okay, go to next step.
  8. Locate and repair cause of TWC failure. Replace TWC. After replacing TWC, go to step  10.
  9. Start engine and run until normal operating temperature is reached. Ensure engine is operating in closed loop. Run engine at 2500-3000 RPM for 3 minutes. Using scan tool, monitor HO2S-1 and HO2S-2 signals. If HO2S-1 signal is as active as HO2S-2 signal, see DIAGNOSTIC AIDS .
  10. Turn ignition on, with engine off. Using scan tool, clear DTC information. Operate vehicle within FREEZE FRAME/FAILURE RECORDS data conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose affected DTCs. See DIAGNOSTIC TROUBLE CODE DEFINITIONS .
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