Subaru Legacy IV (2008 year). Manual - part 617

GD(H6DO)-88

Diagnostic Trouble Code (DTC) Detecting Criteria

GENERAL DESCRIPTION

BN:DTC P0301 CYLINDER 1 MISFIRE DETECTED

1. OUTLINE OF DIAGNOSIS

Detect the presence of misfire occurrence. (Revolution fluctuation method)
Monitoring Misfire which influences exhaust deterioration (1.5 times of FTP) and catalyst damage is made
obligatory by the law. Misfire affecting these two has two patterns below. :
• Intermittent misfire (The same cylinder misfires in random, or different cylinders misfire in random.): FTP
1.5 times misfire
• Every time misfire (The same cylinder misfires every time.): FTP 1.5 times misfire, Catalyst damage mis-
fire
The following detecting methods are adopted for these detection.
1) Intermittent misfire: FTP 1.5 times misfire
• 120° Interval Difference Method
• 360° Interval Difference Method (whole range)
• 720° Interval Difference Method (3,000 rpm or more)
2) Misfire every time: FTP 1.5 times misfire, Catalyst damage misfire
• 360° Interval Difference Method

2. ENABLE CONDITION

Map1

Map2

Secondary Parameters

Enable Conditions

All secondary parameters enable condi-
tions

t 1024 ms

Intake manifold pressure change at
120°CA

< Value of Map 1

Throttle position change during 16 milli-
seconds

< 20 °

Fuel shut-off function

Not in operation

Fuel level

t 9.6

2 (2.54 US gal,

2.11 Imp gal)

Vehicle dynamic control or AT torque
control

Not in operation

Evaporative system leak check

Not in operation

Engine speed

400 rpm — 8000 rpm

Intake manifold pressure

t Value of Map 2

Battery voltage

t 8 V

Fuel parameter determination

Not extremely low vol-
atility

Elapsed time after starting the engine

t 0 ms

Engine speed change during 32 millisec-
onds

< 500 rpm

rpm

700

1000

1500

2000

2500

3000

3500

4000

4500

5000

5500

6000

6500

7000

kPa
(mmHg,
inHg)

(150,

5.9)

(150,

5.9)

(150,

5.9)

(150,

5.9)

(150,

5.9)

(150,

5.9)

(150,

5.9)

(150,

5.9)

(150,

5.9)

(150,

5.9)

(150,

5.9)

(150,

5.9)

(150,

5.9)

(150,

5.9)

rpm

700

1000

1500

2000

2500

3000

3500

4000

4500

5000

5500

6000

6500

7000

kPa
(mmHg,
inHg)

26.7

(200.0,

7.9)

23.3

(175.0,

6.9)

23.3

(175.0,

6.9)

23.3

(175.0,

6.9)

23.6

(177.0,

24.4

(183.0,

7.2)

28.3

(212.5,

8.4)

32.3

(242.2,

9.5)

36.3

(272.0,

10.7)

36.3

(272.0,

10.7)

37.2

(279.0,

11)

38.1

(286.0,

11.3)

41.9

(314.0,

12.4)

48.9

(367.0,

14.4)

GD(H6DO)-89

Diagnostic Trouble Code (DTC) Detecting Criteria

GENERAL DESCRIPTION

3. GENERAL DRIVING CYCLE

• If conditions are met, it is possible to detect the misfires from idling to high engine speed. However, to
avoid excessive load or harm to the engine, perform diagnosis at idle.
• Perform the diagnosis continuously.

4. DIAGNOSTIC METHOD

When a misfire occurs, the engine speed will decreased and the crankshaft position speed will change. Cal-
culate the interval difference value (diagnostic value) from crankshaft position speed by the following formu-
la, and judge whether a misfire is occurring or not comparing the calculated result with judgment value.
Counting the number of misfires. If the misfire ratio is higher during 1000 revs. or 200 revs., Judge corre-
sponding cylinders as NG.

As shown in the following figure, pick a cylinder as the standard and name it omg 0. And the former crank-
shaft position speed is named omg 1, the second former crankshaft position speed is named omg 2, the third
is named omg 3, etc.

Diagnostic value calculation
(Calculate from angle speed)

Misfire detection every single ignition
(Compare diagnostic value with judg-
ment value)

NG judgment (Misfire occurrence judg-
ment required by the law) (Compare
number of misfire with judgment)

• 120° Interval Difference Method
• 360° Interval Difference Method
• 720° Interval Difference Method

• FTP 1.5 times misfire NG judgment
• Catalyst damage misfire NG judgment

(A)

Ignition order

(B)

Crankshaft position speed

EN-02184

(A)

(B)

omg0

omg1

omg2

omg3

omg4

omg5

omg6

omg7

GD(H6DO)-90

Diagnostic Trouble Code (DTC) Detecting Criteria

GENERAL DESCRIPTION

120° Interval Difference Method

360° Interval Difference Method

Diagnostic value domg 120 = (omg 1 – omg 0) – (omg 7 – omg 1)/6

Judge as a misfire in the following cases.

• domg 120 > judgment value of positive side
• domg 121

d judgment value of negative side

(Judgement value before 120° CA)

Diagnostic value domg 360 = (omg 1 – omg 0) – (omg 4 – omg 3)

Misfire judgment domg 360 > Judgement value

o Judge as misfire

EN-02185

Judged as misfire

Threshold value (positive number)

Threshold value (negative number)

domg120

EN-02279

Judged as misfire

Threshold value

domg360

GD(H6DO)-91

Diagnostic Trouble Code (DTC) Detecting Criteria

GENERAL DESCRIPTION

720° Interval Difference Method

• FTP 1.5 times misfire (Misfire occurrence level which influences exhaust gas)

• Abnormality Judgement

Time Needed for Diagnosis: 1000 engine revs.
Malfunction Indicator Light Illumination: Illuminates when malfunction occurs in 2 continuous driving cy-
cles.
• Normality Judgement

Time Needed for Diagnosis: 1000 engine revs.

Diagnostic value domg 720 = (omg 1 – omg 0) – (omg 7 – omg 6)

Misfire judgment domg 720 > Judgement value

o Judge as misfire

Judgement Value (Judge that malfunction occurs when the misfire ratio is high in 1000 engine revs.)

Malfunction Criteria

Threshold Value

FTP emission judgment value

t 27 × 100/3000% in
1000 revs.

Judgement Value

Malfunction criteria

Threshold value

FTP emission judgment value

< 27 × 100/3000% in
1000 revs.

EN-02280

Judged as misfire

Threshold value

domg720

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