Subaru Legacy IV (2008 year). Manual — part 404

GD(H4DOTC)-66

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 CONDITION

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 Conditions

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)

Non-turbo

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)

11.7187

5 (0.41)

14.0625

(0.5)

fsobdL1 (%)

0.6

0.6

0.63137

0.68082

0.73025

0.73025

0.73025

Judgement Value

Malfunction Criteria

Threshold Value

fsobd = (sglmd – tglmda) + faf + flaf

t 0.8

GD(H4DOTC)-67

Diagnostic Trouble Code (DTC) Detecting Criteria

GENERAL DESCRIPTION

AJ:DTC P0181 FUEL TEMPERATURE SENSOR “A” CIRCUIT RANGE/

PERFORMANCE

1. OUTLINE OF DIAGNOSIS

Detect faults in the fuel temperature sensor output properties.
Diagnosis is performed in two methods (drift diagnosis and stuck diagnosis). If either is NG, judge as NG. If
both are OK, Judge as OK and clear the NG.

Drift Diagnosis

Normally fuel temperature is lower than engine coolant temperature. When the fuel temperature becomes
higher than the engine coolant temperature, the range is considered to be shifted, and judged as NG.

Stuck Diagnosis

As the engine warms up (cumulative amount of intake air after starting is large), if the fuel temperature which
should rise does not, determine as being stuck and NG.

2. COMPONENT DESCRIPTION

3. ENABLE CONDITION

DRIFT DIAGNOSIS

4. GENERAL DRIVING CYCLE

Always perform the diagnosis continuously.

(A)

Resistance value (

:)

(B)

Fuel temperature °C (°F)

Secondary Parameters

Enable Conditions

None

EN-01700

(A)

(B)

GD(H4DOTC)-68

Diagnostic Trouble Code (DTC) Detecting Criteria

GENERAL DESCRIPTION

5. DIAGNOSTIC METHOD

• Abnormality Judgement

If the duration of time while the following conditions are met is longer than the time indicated, judge as NG.

Time Needed for Diagnosis: 120 s
Malfunction Indicator Light Illumination: Illuminates when malfunction occurs in 2 continuous driving cy-
cles.

• Normality Judgement

Judge as OK and clear the NG if the continuous time while the following conditions are established is more
than the predetermined time.

Time Needed for Diagnosis: Less than 1 second

6. ENABLE CONDITION

Stuck Diagnosis

7. GENERAL DRIVING CYCLE

Always perform diagnosis after 20 seconds have passed since the engine started.

Judgement Value

Malfunction Criteria

Threshold Value

Fuel level

t 9.6

2 (2.54 US gal,

2.11 Imp gal)

Elapsed time after starting the engine

t 20 s

Engine coolant temperature – Engine
coolant temperature at engine start

> 10 °C (50 °F)

Fuel temperature – Engine coolant tem-
perature

t 10 °C (50 °F)

Battery voltage

t 10.9 V

Judgement Value

Malfunction Criteria

Threshold Value

Fuel level

t 9.6

2 (2.54 US gal,

2.11 Imp gal)

Elapsed time after starting the engine

t 20 s

Engine coolant temperature – Engine
coolant temperature at engine start

> 10 °C (50 °F)

Fuel temperature – Engine coolant tem-
perature

< 10 °C (50 °F)

Battery voltage

t 10.9 V

Engine coolant temperature

< 70 °C (158 °F)

Secondary Parameters

Enable Conditions

Elapsed time after starting the engine

t 20000 ms

Battery voltage

t 10.9 V

GD(H4DOTC)-69

Diagnostic Trouble Code (DTC) Detecting Criteria

GENERAL DESCRIPTION

8. DIAGNOSTIC METHOD

• Abnormality Judgement

Judge as NG when the following conditions are established.

Time Needed for Diagnosis: Less than 1 second
Malfunction Indicator Light Illumination: Illuminates when malfunction occurs in 2 continuous driving cy-
cles.

• Normality Judgement

Judge as OK and clear the NG if the following conditions are established.

Time Needed for Diagnosis: Less than 1 second

Judgement Value

Malfunction Criteria

Threshold Value

Accumulated amount of intake air

t 551043 g (19435.29 oz)

Fuel temperature difference between
Max. and Min.

< 2 °C (35.6 °F)

Judgement Value

Malfunction Criteria

Threshold Value

Fuel temperature difference between
Max. and Min.

t 2 °C (35.6 °F)