DTC P0420 CATALYST SYSTEM EFFICIENCY BELOW THRESHOLD (BANK 1)
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DTC P0420 CATALYST SYSTEM EFFICIENCY BELOW
THRESHOLD (BANK 1)
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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.
(1)
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Front oxygen
(A/F) sensor
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(A)
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Normal
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(C)
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Front oxygen (A/F) sensor waveform
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(2)
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Front oxygen
sensor
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(B)
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Deterioration
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(3)
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Catalyst
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(D)
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Front oxygen
sensor waveform
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Secondary
Parameters
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Enable
Conditions
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Battery
voltage
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> 10.9
V
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Atmospheric
pressure
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> 75.1
kPa (563 mmHg, 22.2 inHg)
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Engine
coolant temperature
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≥ 70°C
(158°F)
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Catalyst
warm-up counter on Map 2
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≥ 8000
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Misfire
detection during 200 engine revs.
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< 5
times
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Learning
value of evaporation gas density
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≤ 0.20
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Sub
feedback
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Operating
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Evaporative
system diagnostic
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Not
in operation
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Difference
between actual and target time lambda < 0.10
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1000
milliseconds or more
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Vehicle
speed
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> 70
km/h (43.5 MPH)
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Amount
of intake air
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10 ←→ 40
g (0.35 ←→ 1.41 oz)/s
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Engine
load change every 0.5 engine revs.
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< 0.02
g/rev
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Rear
O
2
output change from below 660 mV to over
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Experienced
after fuel cut
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After
engine starting
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≥ 250
seconds
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Purge execution
cumulative time
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5 seconds
or more
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Map 2
Add the following value every 512 milliseconds.
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Amount
of intake air (g (oz)/s)
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0
(0)
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3.2 (0.113)
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6.4 (0.226)
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9.6 (0.339)
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12.8 (0.451)
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16 (0.564)
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19.2 (0.677)
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22.4 (0.790)
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25.6 (0.903)
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28.8 (1.016)
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32 (1.129)
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35.2 (1.242)
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Integrated
value for warm-up counter
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−8
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−8
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20
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32
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52
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82
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113
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143
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173
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204
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234
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264
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Perform the diagnosis once at the constant
vehicle speed 70 km/h (43 MPH).
After the malfunction criteria are completed,
calculate cumulative value of front oxygen (A/F) sensor
lambda deviation (Σ |(sglmd
n
− sglmd
n-1
)|) every 128 milliseconds and cumulative
value of rear oxygen 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
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Malfunction
Criteria
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Threshold
Value
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Σ |(ro2sad
n
− ro2sad
n-1
)| / Σ |(sglmd
n
− sglmd
n-1
)|
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> 7.5
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Time Needed for Diagnosis:
30 — 55
seconds
Malfunction Indicator
Light Illumination:
Illuminates when malfunction occurs in
2 continuous driving cycles.
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•
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When the OK idling cycle was completed 40 times
in a row
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•
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When “Clear Memory” was
performed
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MALFUNCTION
INDICATOR LIGHT CLEAR CONDITION
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•
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When the OK driving cycle was completed 3 times
in a row
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•
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When “Clear Memory” was
performed
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None
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ECM OPERATION
AT DTC SETTING
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Memorize the freeze frame data. (For test mode $02)
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•
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Memorize the diagnostic value and trouble
standard value. (For test mode $06)
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