P0420

DTC P0420 CATALYST SYSTEM EFFICIENCY BELOW THRESHOLD (BANK 1)

1. OUTLINE OF DIAGNOSIS
Detect the deterioration of the catalyst function.
Though the front oxygen sensor output would change slowly with a new catalyst, the sensor output with a deteriorated catalyst becomes high and the inversion time is shortened.
For this reason, the catalyst diagnosis is carried out by monitoring the front oxygen sensor output and comparing it with the front oxygen (A/F) sensor output.




2. COMPONENT DESCRIPTION







3. ENABLE CONDITION

4. GENERAL DRIVING CYCLE
Perform the diagnosis only once at a constant speed of 70 km/h (43 MPH).




5. DIAGNOSTIC METHOD
After establishing the execution conditions, calculate the front oxygen (A/F) sensor lambda deviation cumulative value per 128 milliseconds (Sigma |(sglmdn - sglmdn- 1 )|) and rear oxygen sensor output voltage deviation cumulative value (Sigma |(ro2sadn - ro2sadn- 1)|), and when the front oxygen (A/F) sensor lambda deviation cumulative value (Sigma |(sglmdn - sglmdn- 1)|) becomes higher than the predetermined value, calculate the diagnostic value.
Judge as NG when the malfunction criteria below are met. Judge as OK if the criteria below are not met.

6. DTC CLEAR CONDITION
- When the OK idling cycle is completed 40 times in a row
- When "Clear Memory" is performed

7. MALFUNCTION INDICATOR LIGHT CLEAR CONDITION
- When the OK driving cycle is completed 3 times in a row
- When "Clear Memory" is performed

8. FAIL SAFE
None

9. ECM OPERATION AT DTC SETTING
- Memorize the freeze frame data. (For test mode $02)
- Memorize the diagnostic value and trouble standard value. (For test mode $06)