Subaru 2009 IMPREZA, Service Manual

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GD(H4DOTC)-67
Diagnostic Trouble Code (DTC) Detecting Criteria
GENERAL DESCRIPTION
AI: DTC P0172 SYSTEM TOO RICH (BANK 1)
1. OUTLINE OF DIAGNOSIS
Detect 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.
2. ENABLE CONDITIONS
3. GENERAL DRIVING CYCLE
Perform the diagnosis continuously at idling or at a constant speed after warming up the engine.
4. DIAGNOSTIC METHOD
• Abnormality Judgement
Compare the diagnosed value (fsobd) with the threshold value, and if a condition meeting the malfunction cri-
teria below continues for 10 s × 5 time(s) or more, judge that there is a fault in the fuel system.
Time Needed for Diagnosis: 10 s × 5 time(s)
Malfunction Indicator Light Illumination: Illuminates when malfunction occurs in 2 continuous driving cycles.
• Normality Judgement
Judge as OK when the malfunction criteria below continues for 10 seconds.
Time Needed for Diagnosis: 10 s
Secondary Parameters Enable Condition
A/F main learning system In operation
Engine coolant temperature
t
70 °C (158 °F)
Engine load change
d
0.02 g/rev (0 oz/rev)
Learning value of EVAP conc. < 0.1
Cumulative time of canister purge after engine start
t
20 s
Continuous period after canister purge starting
t
29884 ms
Engine load
t
Value of Map 1
Map1
Engine speed (rpm) Idling 800 1200 1600 2000 2400 2800 3200 3600 4000 4400
Measured value (g(oz)/rev) na
0.228
(0.01)
0.22
(0.01)
0.22
(0.01)
0.22
(0.01)
0.228
(0.01)
0.23
(0.01)
0.234
(0.01)
0.242
(0.01)
0.25
(0.01)
0.25
(0.01)
Judgement Value
Malfunction Criteria Threshold Value
fsobd = (sglmd – tglmda) + faf + flaf < Value of Map 2
In this case: sglmd = measured lambda
tglmda = target lambda
faf = main feedback compensation coefficient every
64 milliseconds
flaf = main feedback learning compensation
coefficient
Map2
Amount of air (g (oz)/s) 0 (0)
2.34375
(0.08)
4.6875
(0.17)
7.03125
(0.25)
9.375
(0.33)
11.71875
(0.41)
14.0625
(0.5)
fsobdL1 (%) 0.6 0.6 0.63137 0.68082 0.71025 0.72525 0.73025
Judgement Value
Malfunction Criteria Threshold Value
fsobd = (sglmd – tglmda) + faf + flaf
t
0.8