DTC P0171 SYSTEM TOO LEAN (BANK 1)
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DTC P0171 SYSTEM TOO LEAN (BANK 1)
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Detect the fuel system malfunction by the
amount of main feedback control.
Diagnostic Method
Fuel system is diagnosed by comparing the
target air fuel ratio calculated by ECM with the actual air fuel
ratio measured by sensor.
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•
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Lean side
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Secondary
Parameters
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Enable
Conditions
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A/F
main learning system
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In
operation
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Engine
coolant temperature
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≥ 70°C
(158°F)
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Intake
air amount
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≥ Map
5
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Intake
air change during 0.5 engine rev.
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≤ 0.02
g (0.001 oz)/rev
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Map 5
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Engine
speed (rpm)
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idle
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650
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1000
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1500
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2000
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2500
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3000
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3500
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4000
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4500
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Measured
value (g (oz)/rev)
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NA
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0.201 (0.007)
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0.150 (0.005)
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0.150 (0.005)
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0.156 (0.006)
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0.161 (0.006)
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0.157 (0.006)
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0.167 (0.006)
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0.184 (0.006)
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0.198 (0.007)
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Perform the diagnosis continuously at engine
idling after warm-up or a constant speed.
Abnormality Judgment
Judge that the fuel system malfunction occurs
when the time during completing the malfunction criteria below continues
50 seconds or more by comparing the diagnosed value (fsobd) with
threshold value.
Judgment
Value
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Malfunction
Criteria
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Threshold
Value
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fsobd = (sglmd − tglmda) + faf + flaf
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≥ fsobdL1
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where,
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See
Map 4
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sglmd = measured
lambda
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tglmda = target
lambda
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fsobdL1 = lean
side threshold value of fsobd
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faf = main
feedback compensation coefficient every 64 milliseconds
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flaf = main
feedback learning compensation coefficient
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Map 4 Threshold value for fuel system malfunction
criteria
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Amount
of 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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fsobdL1
(%)
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40
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40
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33.2
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26.5
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26.5
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26.5
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26.5
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Time Needed for Diagnosis:
10
seconds × 5 times
Malfunction Indicator
Light Illumination:
Illuminates when malfunction occurs in
2 continuous driving cycles.
Normality Judgment
Judge OK when the malfunction criteria below
are continued for 10 seconds.
Judgment
Value
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Malfunction
Criteria
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Threshold
Value
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fsobd = (sglmd − tglmda) + faf + flaf
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< 19%
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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 OK with similar drive in 3 driving cycles.
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•
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When “Clear Memory” was
performed
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None
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ECM OPERATING
AT DTC SETTING
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Memorize the freeze frame data. (For test
mode $02)
