P0431 Warm up catalyst Efficiency Below Threshold (bank 2)
The signal from the rear heated oxygen sensor differs from the front heated oxygen sensor. That is because the catalytic converter purifies exhaust gas. When the catalytic converter has deteriorated, the signal from the front heated oxygen sensor becomes similar to the rear heated oxygen sensor.
The PCM compares the output of the front and rear heated oxygen sensor signals.
Check Conditions
Engine speed is lower than 3,000 r/min.
The throttle valve is open.
Volume airflow sensor output frequency is between 69 and 169 Hz.
More than 3 seconds has elapsed after the above-mentioned three conditions have been met.
Intake air temperature is higher than −10°C (14°F).
Barometric pressure is higher than 76 kPa (11 psi).
Under the closed loop air/fuel ratio control.
Vehicle speed is 1.5 km/h (0.93 mph) or more.
The PCM monitors for this condition for 7 cycles of 12 seconds each during the drive cycle.
Short-term fuel trim is higher than −30 percent and lower than +25 percent.
The cumulative volume airflow sensor output frequency for every 2 seconds is higher than 4,000 Hz.
Judgment Criteria
The left bank heated oxygen sensor (rear) signal frequency divided by left bank heated oxygen sensor (front) signal frequency = 0.75 or more.
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are: )
- Left bank side catalytic converter deteriorated.
- Left bank heated oxygen sensor failed.
- PCM failed.
The signal from the rear heated oxygen sensor differs from the front heated oxygen sensor. That is because the catalytic converter purifies exhaust gas. When the catalytic converter has deteriorated, the signal from the front heated oxygen sensor becomes similar to the rear heated oxygen sensor.
The PCM compares the output of the front and rear heated oxygen sensor signals.
Check Conditions
Engine speed is lower than 3,000 r/min.
The throttle valve is open.
Volume airflow sensor output frequency is between 69 and 169 Hz.
More than 3 seconds has elapsed after the above-mentioned three conditions have been met.
Intake air temperature is higher than −10°C (14°F).
Barometric pressure is higher than 76 kPa (11 psi).
Under the closed loop air/fuel ratio control.
Vehicle speed is 1.5 km/h (0.93 mph) or more.
The PCM monitors for this condition for 7 cycles of 12 seconds each during the drive cycle.
Short-term fuel trim is higher than −30 percent and lower than +25 percent.
The cumulative volume airflow sensor output frequency for every 2 seconds is higher than 4,000 Hz.
Judgment Criteria
The left bank heated oxygen sensor (rear) signal frequency divided by left bank heated oxygen sensor (front) signal frequency = 0.75 or more.
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are: )
- Left bank side catalytic converter deteriorated.
- Left bank heated oxygen sensor failed.
- PCM failed.