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Home >> Isuzu >> 2000 >> Rodeo LSE, 2.2 D >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics - 2.2L >> Diagnostic Trouble Code Identification >> DTC P0420: TWC System Low Efficiency >> Diagnostic Procedures

Diagnostic Procedures

  1. Perform On-Board Diagnostic II (OBD-II) system check. See SELF-DIAGNOSTICS - INTRODUCTION article. Go to next step.
  2. Diagnose any other HO2S DTC(s) set before proceeding. If no other HO2S DTCs are set, go to next step.
  3. Ensure TWC is an original equipment part. Check TWC for dents, or discoloration caused by excessive heat. Ensure no internal damage or catalyst rattle exists. If a problem is found, repair as necessary and go to step  6. If no problems are found, go to next step.
  4. Check exhaust system for leaks, damage, loose or missing hardware. If a problem is found, repair as necessary and go to step  7. If no problems are found, go to next step.
  5. Ensure HO2S-2 is securely installed and that harness is not damaged or contacting exhaust. If a problem is found, repair as necessary and go to step  7. If no problems are found, go to next step.
  6. Replace TWC. Check for possible engine misfire DTCs or engine mechanical problem, and go to next step.
  7. Read and record FAILURE RECORDS data for DTC P0420. Clear DTCs. Start engine and allow it to idle until cooling system temperature is greater than 140°F (60°C). Run engine (while monitoring scan tool IAC RPM control function) to maintain MAF at 7-41 grams per second for at least 2 minutes. Using scan tool, monitor TWC MONITOR TEST COUNTER while operating vehicle within conditions required to set DTC. Continue operating vehicle until TWC MONITOR TEST COUNTER reaches 49 and returns to zero 2 times. Read specified DTC. If scan tool displays DTC P0420 TEST RAN AND PASSED, repair is complete. If scan tool does not display DTC P0420 TEST RAN AND PASSED, return to step  2.
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