Code No. P0431: Warm Up Catalyst Malfunction (Cylinder 2, 3) <Vehicles for Hong kong>

FUNCTION

The signal from the cylinder 2, 3 oxygen sensor (rear) differs from the cylinder 2, 3 oxygen sensor (front). That is because the catalytic converter purifies exhaust gas. When the catalytic converter has deteriorated, the signal from the cylinder 2, 3 oxygen sensor (front) becomes similar to the cylinder 2, 3 oxygen sensor (rear).

The engine-A/T-ECU compares the output of the cylinder 2, 3 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 Criteria

The cylinder 2, 3 oxygen sensor (rear) signal frequency divided by cylinder 2, 3 oxygen sensor (front) signal frequency is 0.8 or more.

PROBABLE CAUSE

Catalytic converter deteriorated

Failed cylinder 2, 3 oxygen sensor (front)

Failed cylinder 2, 3 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 39: Cylinder 2, 3 oxygen sensor (front)

Item 69: Cylinder 2, 3 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 39: Cylinder 2, 3 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 2, 3 oxygen sensor (front).

STEP 4. Replace the cylinder 2, 3 oxygen sensor (rear).

After replacing the cylinder 2, 3 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 2, 3).

After replacing the catalytic converter (cylinder 2, 3), re-check the trouble symptoms.

Q: Is the check result normal?

YES: Replace engine-A/T-ECU.
NO: Check end.


Code No. P0431: Warm Up Catalyst Malfunction (Cylinder 2, 3) <Vehicles for Hong kong>

FUNCTION The signal from the cylinder 2, 3 oxygen sensor (rear) differs from the cylinder 2, 3 oxygen sensor (front). That is because the catalytic converter purifies exhaust gas. When the catalytic converter has deteriorated, the signal from the cylinder 2, 3 oxygen sensor (front) becomes similar to the cylinder 2, 3 oxygen sensor (rear). The engine-A/T-ECU compares the output of the cylinder 2, 3 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 Criteria The cylinder 2, 3 oxygen sensor (rear) signal frequency divided by cylinder 2, 3 oxygen sensor (front) signal frequency is 0.8 or more.
PROBABLE CAUSE Catalytic converter deteriorated Failed cylinder 2, 3 oxygen sensor (front) Failed cylinder 2, 3 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 39: Cylinder 2, 3 oxygen sensor (front) Item 69: Cylinder 2, 3 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 39: Cylinder 2, 3 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 2, 3 oxygen sensor (front).
	STEP 4. Replace the cylinder 2, 3 oxygen sensor (rear). After replacing the cylinder 2, 3 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 2, 3). After replacing the catalytic converter (cylinder 2, 3), re-check the trouble symptoms. Q: Is the check result normal? YES: Replace engine-A/T-ECU. NO: Check end.