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Home >> Honda >> 2000 >> CR-V SE, Standard >> Repair and Diagnosis >> External Pages >> Different car >> Section 10 (Engine Controls - Self-Diagnostics - 4.3L) >> Diagnostic Trouble Code Identification >> DTC P0420: TWC System Low Efficiency Bank 1 >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different car, the 2000 Isuzu Hombre. However, it is still accessible from the selected car via links, so may be relevant.
  1. Perform On-Board Diagnostic II (OBD-II) System Check. See SELF-DIAGNOSTICS - INTRODUCTION article. Retrieve and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. Go to next step.
  2. Diagnose any other DTCs before proceeding. If no other DTCs are set, go to next step.
  3. Check for and repair the following condition(s):
    • Ensure TWC is an O.E. part.
    • Check TWC for damage.
    • Ensure no internal damaged catalyst rattle exists.
    • Check exhaust system for leaks, damage, loose or missing hardware.
    • Ensure HO2S bank 1 sensor 3 is securely installed, and harness and connector are not damaged or contacting exhaust.

    If problem is found, go to step  9. If no problem is found, go to next step.

  4. Check all VCM ground circuits. See WIRING DIAGRAMS article. If problem is found, go to step  9. If no problem is found, go to next step.
  5. Check all sensor ground circuits (Black wires). If problem is found, to step  9. If no problem is found, go to next step.
  6. Check HO2S bank 1 sensor 3 signal circuit (Purple/White wire) and ground circuit (Black wire) for intermittent opens. If problem is found, go to step  9. If no problem is found, go to next step.
  7. Check HO2S bank 1 sensor 3 signal circuit (Purple/White wire) and ground circuit (Black wire) for intermittent short to ground. If problem is found, go to step  9. If no problem is found, go to next step.
  8. Replace TWC. Check for possible engine misfire DTC or engine mechanical problem. After repairs, go to step  10.
  9. Repair wiring or connection problem(s) as necessary. After repairs, go to next step.
  10. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter DTC P0420. Operate vehicle within conditions required to set DTC. If scan tool displays RAN AND PASSED, go to next step. If scan tool does not display RAN AND PASSED, return to step  2.
  11. Using scan tool, select Read and Record INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, diagnose affected DTCs. If no DTCs are displayed, system is okay.
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