P0420 (U5/Low Emissions)

DTC P0420 - CATALYST SYSTEM EFFICIENCY BELOW THRESHOLD (BANK 1)

OUTLINE OF DIAGNOSIS
Detect the deterioration of 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 A/F sensor output.




COMPONENT DESCRIPTION




ENABLE CONDITION

GENERAL DRIVING CYCLE
Perform the diagnosis once at the constant vehicle speed 70 km/h (43 MPH).

DIAGNOSTIC METHOD




After the malfunction criteria are completed, calculate the output fluctuation value of front oxygen (A/F) sensor (with right and left) and output fluctuation value of front oxygen sensor (with right and left).
Calculate the diagnosis value when the front oxygen (A/F) sensor output fluctuation value more than specified value. (With right and left)
Diagnostic values on both sides are added and total is considered as a final diagnostic value.
Judge NG when the malfunction criteria are completed, and judge OK when they are not completed.

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

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

FAIL SAFE
None

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)