[13C] MULTIPORT FUEL INJECTION (MPI) <4G69> - - TROUBLESHOOTING - INSPECTION PROCEDURE FOR DIAGNOSIS CODES - Code No. P0421: Warm Up Catalyst Malfunction (cylinder 1,4) <Vehicles for Hong kong> | PRINT PAGE / INDEX / PRIOR / NEXT

Code No. P0421: Warm Up Catalyst Malfunction (cylinder 1,4) <Vehicles for Hong kong>
FUNCTION The signal from the cylinder 1, 4 oxygen sensor (rear) differs from the cylinder 1, 4 oxygen sensor (front). That is because the catalytic converter purifies exhaust gas. When the catalytic converter has deteriorated, the signal from the cylinder 1, 4 oxygen sensor (front) becomes similar to the cylinder 1, 4 oxygen sensor (rear). The engine-A/T-ECU compares the output of the cylinder 1, 4 oxygen sensor signals (front and rear).
TROUBLE JUDGMENT Check Conditions Engine speed is 3,000 r/min or lower. The accelerator pedal is open. Air flow sensor output is 8 gm/s or higher. 3 seconds or more elapsed after the abovementioned conditions were satisfied. Intake air temperature is -10°C or higher after the engine is started. Barometric pressure is 76 kPa or higher. Under the closed loop air/fuel ratio control. Vehicle speed is 1.5 km/h or higher. For 10 seconds per cycle, the engine-A/T-ECU monitors 7 cycles of this condition during the drive cycle. Short-term fuel trim is between -25% or higher and +25% or lower. The cumulative air flow sensor output is 2,931 g or higher. Judgment Criterion The cylinder 1, 4 oxygen sensor (rear) signal frequency divided by cylinder 1, 4 oxygen sensor (front) signal frequency is 0.8 or more.
PROBABLE CAUSE Catalytic converter deteriorated Failed cylinder 1, 4 oxygen sensor (front) Failed cylinder 1, 4 oxygen sensor (rear) Failed engine-A/T-ECU
| DIAGNOSIS PROCEDURE
| STEP 1. Check for leakage of exhaust emission from exhaust manifold. Q: Is the check result normal? YES: Go to Step 2 . NO: Repair.
| STEP 2. MUT-II/III data list Refer to Data List Reference Table . Item 11: Cylinder 1, 4 oxygen sensor (front) Item 59: Cylinder 1, 4 oxygen sensor (rear) Q: Is the check result normal? YES: Go to Step 3 . NO: Perform the diagnosis code classified check procedure for the sensor that has shown an abnormal data valve (Refer to Inspection Chart for Diagnosis Code ).
| STEP 3. MUT-II/III data list Item 11: Cylinder 1, 4 oxygen sensor (front) OK: 0 - 0.4 and 0.6 - 1.0 volt should alternate 15 times or more within 10 seconds (engine speed at 2,000 r/min). Q: Is the check result normal? YES: Go to Step 4 . NO: Replace the cylinder 1, 4 oxygen sensor (front).
| STEP 4. Replace the cylinder 1, 4 oxygen sensor (rear). After replacing the cylinder 1, 4 oxygen sensor (rear), re-check the trouble symptoms. Q: Is the check result normal? YES: Check end. NO: Go to Step 5 .
| STEP 5. Replace the catalytic converter (cylinder 1, 4). After replacing the catalytic converter (cylinder 1, 4), re-check the trouble symptoms. Q: Is the check result normal? YES: Replace engine-A/T-ECU. NO: Check end.

[13C] MULTIPORT FUEL INJECTION (MPI) <4G69> - - TROUBLESHOOTING - INSPECTION PROCEDURE FOR DIAGNOSIS CODES - Code No. P0421: Warm Up Catalyst Malfunction (cylinder 1,4) <Vehicles for Hong kong> | PRINT PAGE / INDEX / PRIOR / NEXT

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