Subaru 2009 IMPREZA Service Manual page 790

Diagnostic Trouble Code (DTC) Detecting Criteria
GENERAL DESCRIPTION
AK: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
Secondary Parameters
A/F main learning system
Engine coolant temperature
Engine load change
Learning value of EVAP conc.
Cumulative time of canister purge after engine start
Continuous period after canister purge starting
Engine load
Map 1
Engine speed (rpm)
Measured value (g(oz)/rev)
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.
Judgement Value
Malfunction Criteria
fsobd = (sglmd – tglmda) + faf + flaf
In this case: sglmd = measured lambda
tglmda = target lambda
faf = main feedback compensation coefficient every
64 milliseconds
flaf = main feedback learning compensation coeffi-
cient
Map 2
Amount of air (g (oz)/s)
fsobdL1 (%)
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.
Judgement Value
Malfunction Criteria
fsobd = (sglmd – tglmda) + faf + flaf
Time Needed for Diagnosis: 10 s
In operation
75 °C (167 °F)
0.02 g/rev (0 oz/rev)
< 0.15
20 s
29884 ms
Value of Map 1
Idling 650 1000
0.208 0.201
na
(0.01) (0.01)
< Value of Map 2
3.2 6.4
0 (0)
(0.11) (0.23)
0.6 0.6 0.668
0.8
GD(H4SO)-66
Enable Condition
1500 2000 2500
0.185 0.183 0.193
(0.01) (0.01) (0.01)
Threshold Value
9.6 12.8 16
(0.34) (0.45) (0.56)
0.735 0.735 0.735
Threshold Value
3000 3500 4000
0.206 0.206 0.225
(0.01) (0.01) (0.01)
19.2
(0.68)
0.735
4500
0.245
(0.01)