P0420

DTC P0420 CATALYST SYSTEM EFFICIENCY BELOW THRESHOLD (BANK 1)

1. OUTLINE OF DIAGNOSIS
Detect the deterioration of the catalyst function.

Though the rear 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 rear oxygen sensor output and comparing it with the front oxygen A/F sensor output.

2. COMPONENT DESCRIPTION






3. ENABLE CONDITION

Enable Conditions:

4. GENERAL DRIVING CYCLE
Perform the diagnosis only once at a constant vehicle speed of 75 km/h (47 MPH) after warming up.

5. DIAGNOSTIC METHOD
After the execution criteria are established, calculate the output fluctuation value of front oxygen (A/F) sensor and output fluctuation value of rear oxygen sensor. Calculate the diagnosis value when the front oxygen (A/F) sensor output fluctuation value is more than specified value. A/F response properties and diagnosis values are parameters for the judgment value.

Judge as NG when the malfunction criteria below are met. Judge as OK if the criteria below are not met.






Time Needed for Diagnosis: 33 - 55 seconds

Malfunction Indicator Light Illumination: Illuminates when malfunction occurs in 2 continuous driving cycles.

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)