DTC P0420 CATALYST SYSTEM EFFICIENCY BELOW THRESHOLD (BANK 1)

DTC P0420 CATALYST SYSTEM EFFICIENCY BELOW THRESHOLD (BANK 1)

(1)	Front oxygen (A/F) sensor	(A)	Normal
(2)	Rear oxygen sensor	(B)	Deterioration
(3)	Catalyst	(C)	Front oxygen (A/F) sensor waveform
		(D)	Rear oxygen sensor waveform

ENABLE CONDITION

Secondary Parameters	Enable Conditions
Battery voltage	> 10.9 V
Atmospheric pressure	> 75.1 kPa (563 mmHg, 22.2 inHg)
Engine coolant temperature	≥ 65°C (149°F)
Catalyst warm-up counter on Map 2	≥ 7,600
Misfire detection during 200 engine revs.	< 5 times
Learning value of evaporation gas density	< 0.20
Sub feedback	Operating
Evaporative system diagnostic	Not in operation
Difference between actual and target time lambda < 0.10	1,000 milliseconds or more
Vehicle speed	≥ 75 km/h (46.6 MPH)
Engine speed	1,600 ←→ 3,500 rpm
Amount of intake air	10 ←→ 36 g/s
Engine load change every 0.5 engine revs.	< 0.03 g/rev
Rear O 2 output change from Lean to Rich	Experienced after fuel cut

Map 2

Add the following value every 524.288 milliseconds.

Catalyst warm-up counter ≤ 7,500

Amount of intake air (g/s)	0	4.7	9.4	14.1	18.8	23.4	28.1	32.8	37.5	42.2	46.9	51.6
Integrated value for warm-up counter	−15.7	−1	15.9	31.7	47.5	63.3	79.1	94.8	111	126	126	126

Catalyst warm-up counter > 7,500

Amount of intake air (g/s)	0	4.7	9.4	14.1	18.8	23.4	28.1	32.8	37.5	42.2	46.9	51.6
Integrated value for warm-up counter	−5.3	−2	6.3	8.4	9.9	11.0	12.0	12.8	13.5	14.1	14.6	15.1

GENERAL DRIVING CYCLE

Perform the diagnosis once at the constant vehicle speed from 80 to 100 km/h (49.7 to 62.1 MPH).

DIAGNOSTIC METHOD

After the malfunction criterias are completed, calculate cumulative value of front oxygen (A/F) sensor lambda deviation (Σ |(sglmd _n − sglmd _n-1 )|) and cumulative value of rear oxygen (A/F) sensor output voltage deviation (Σ |(ro2sad _n − ro2sad _n-1 )|).

Calculate the diagnosis value when the front oxygen (A/F) sensor output fluctuation value more than specified value.

Judge NG when the malfunction criteria below are completed, and judge OK when they are not completed.

Judgment Value

Malfunction Criteria	Threshold Value
Σ |(ro2sad n − ro2sad n-1 )| / Σ |(sglmd n − sglmd n-1 )|	≥ 4

Map 3

Diagnosis value	0.15	0.2	0.25	0.3
Judgment value	4	6.5	9	12

Time Needed for Diagnosis: 30 — 55 seconds

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

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)