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TROUBLESHOOTING MULTIPORT FUEL INJECTION (MFI) 13A-147 Code No. P0420: Catalyst malfunction FUNCTION The signal from the heated oxygen sensor (rear) The engine-ECU compares the output of the front TROUBLE JUDGMENT Check Conditions Engine speed: 3,000 r/min or less. During the driving. During the air-fuel ratio feedback control. Judgment Criterion When the output frequency ratio of the oxygen PROBABLE CAUSE Catalytic converter deteriorated Failed oxygen sensor (front) Failed oxygen sensor (rear) Failed engine-ECU DIAGNOSIS PROCEDURE STEP 1.Check for leakage of exhaust emission Q: Is the check result normal? YES : Go to Step 2 . NO : Repair. STEP 2.MUT-II data list Refer to Data list reference table
a. Item 11: Oxygen sensor (front) Q: Is the check result normal? YES : Go to Step 3 . NO : Perform the diagnosis code classified check ). STEP 3.MUT-II data list a. Item 11: Oxygen sensor (front) OK: 0 - 0.4 and 0.6 - 1.0 volt should alternate 15 times or more within 10 seconds (engine Q: Is the check result normal? YES : Go to Step 4 . NO : Replace the oxygen sensor (front). STEP 4.Replace the oxygen sensor (rear). After replacing the oxygen sensor (rear), re- Q: Is the check result normal? YES : Go to Step 5 . NO : Check end. STEP 5.Replace the catalytic converter. After replacing the catalytic converter, re-check Q: Is the check result normal? YES : Replacing engine-ECU. NO : Check end. |