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Home >> Acura >> 2003 >> MDX Base >> Repair and Diagnosis >> Engine Performance >> System >> Engine Performance System Self-Diagnostics >> Diagnostic Tests >> DTC P0420 Or DTC P0430
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DTC P0420 Or DTC P0430

Code Definition

CAUTION: When substituting or replacement of PCM is recommended, see PCM REMOVAL & REPLACEMENT  for important precautions.
NOTE: This test covers both "REAR" and "FRONT" bank catalytic converter malfunctions. The information will be shown "REAR" first and "FRONT" second. When discussion arises, "REAR" bank catalytic converter will precede "FRONT" bank catalytic converter. Furthermore "FRONT" bank catalytic converter information will be enclosed in parantheses ( ).
NOTE: If DTCs P0137, P0138, P0141, P0161, P0157, or P0158 are set, troubleshoot these codes before proceeding.
NOTE: When poor fuel quality is used, this DTC may be set.
  1. Turn ignition on. Using Honda PGM Tester or the HDS, do the DTC CLEAR in the CLEAR menu.
  2. Start engine. Hold at 3000 RPM with no load (A/T in Park or Neutral) until radiator fan comes on, then let it idle.
  3. Test drive vehicle under the following conditions:
    • Engine coolant temperature more than 158°F (70°C).
    • A/T in "D" position.
    • Vehicle speed between 50-55 MPH with cruise control.
    • Drive about 2 minutes, then decelerate for at least 4 seconds with throttle completely closed, then accelerate to 55 MPH for 20 minutes with cruise control.
  4. Using the Honda PGM Tester or the HDS, monitor OBD STATUS for DTC P0420 and/or (P0430) in the DTCs menu. If it is EXECUTING, continue driving condition until a result comes in. If it is not EXECUTING, go to step  3 and recheck.
  5. Using the Honda PGM Tester or the HDS, monitor OBD STATUS for DTC P0420 and/or (P0430) in the DTCs menu. If it is PASSED, problem is intermittent, system is OK at this time. If it FAILED, go to next step. If it is EXECUTING, continue driving condition until a result comes in. If it is OUT OF CONDITION, go to step  4 and recheck.
  6. Turn ignition off.
  7. Replace the WU-TWC.
  8. Turn ignition on. With the Honda PGM tester or the HDS, do PCM RESET in the CLEAR menu. Do the PCM idle learn procedure. See PCM IDLE LEARN PROCEDURE  . Go to next step.
  9. Start engine. Hold at 3000 RPM with no load (A/T in Park or Neutral) until radiator fan comes on, then let it idle.
  10. Test drive vehicle for about 10 minutes, changing vehicle speeds frequently.
  11. With the Honda PGM tester or the HDS, check the CAT MON TEMP in the DATA list. If it is OK, go to next step. If it is not OK, go to step  9 and recheck.
  12. Test drive vehicle under the following conditions:
    • Engine coolant temperature more than 158°F (70°C).
    • A/T in "D" position.
    • Vehicle speed between 50-55 MPH with cruise control.
    • Drive about 2 minutes, then decelerate for at least 4 seconds with throttle completely closed, then accelerate to 55 MPH for 20 minutes with cruise control.
  13. Using the Honda PGM Tester or the HDS, monitor OBD STATUS for DTC P0420 and/or (P0430) in the DTCs menu. If it is EXECUTING, continue driving condition until a result comes in. If it is not EXECUTING, go to step  12 and recheck.
  14. Check for Temporary DTCs or DTCs in the DTC menu. If Temporary DTCs or DTCs are set, go to indicated DTC and troubleshoot. If Temporary DTCs or DTCs are not set, go to next step.
  15. Using the Honda PGM Tester or the HDS, monitor OBD STATUS for DTC P0420 and/or (P0430) in the DTCs menu. If it is PASSED, troubleshooting is done. If it is FAILED, check the fuel quality. If it is EXECUTING, continue driving condition until a result comes in. If it is OUT OF CONDITION, go to step  12 and recheck.
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