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Home >> Chevrolet >> 2000 >> Tracker 4D Utility, RWD, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System Self-Diagnostics >> Diagnostic Tests >> DTC P0420: Catalyst System Low Efficiency >> Diagnostic Procedures
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Diagnostic Procedures

  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
  2. Check if any HO2S related DTCs are set. If DTC P0131, P0132, P0133, P0134, P0135, P0136 or P0141 is set, diagnose affected DTCs first. If DTC P0131, P0132, P0133, P0134, P0135, P0136 or P0141 is not set, go to next step.
  3. Install scan tool. Warm engine to normal operating temperature. Ensure engine is operating in closed-loop. Operate engine at 2500-3000 RPM for 3 minutes. Using scan tool, monitor HO2S No. 1 and No. 2 signal voltage. If HO2S No. 2 signal is as active as HO2S No. 1 signal, go to step  5. If HO2S No. 2 signal is not as active as HO2S No. 1 signal, go to next step.
  4. Turn ignition on, with engine off. Using scan tool, clear DTCs. Operate vehicle within FREEZE FRAME conditions. Retrieve DTCs. If this DTC resets, go to next step. If this DTC does not reset, see DIAGNOSTIC AIDS .
  5. Check TWC for physical damage (discoloration, holes, dents, internal rattles, etc.). If damage exists, go to step  8. If no damage exists, go to next step.
  6. Check exhaust system for leaks, damage, and loose or missing hardware. Repair as necessary. After repairs, go to step  9. If exhaust system is okay, go to next step.
  7. Check HO2S No. 2 for pigtail and wiring harness contacting exhaust pipe, looseness or road damage. Repair as necessary. After repairs, go to step  9. If HO2S No. 2 is okay, go to next step.
    8. NOTE: Locate and repair cause of TWC failure before installing replacement TWC.
  8. Replace TWC. After repairs, go to step  10.
  9. Start engine. Warm engine to normal operating temperature. Ensure engine is operating in closed-loop. Operate engine at 2500-3000 RPM for 3 minutes. Using scan tool, monitor HO2S No. 1 and No. 2 signal voltage. If HO2S No. 2 signal is as active as HO2S No. 1 signal, go to DIAGNOSTIC AIDS . If HO2S No. 2 signal is not as active as HO2S No. 1 signal, go to next step.
  10. After repairs, clear DTCs. Operate vehicle within FREEZE FRAME conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).
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