Subaru Legacy IV (2008 year). Service 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)
20
(150,
5.9)
20
(150,
5.9)
20
(150,
5.9)
20
(150,
5.9)
20
(150,
5.9)
20
(150,
5.9)
20
(150,
5.9)
20
(150,
5.9)
20
(150,
5.9)
20
(150,
5.9)
20
(150,
5.9)
20
(150,
5.9)
20
(150,
5.9)
20
(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,
7)
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)
o
Misfire detection every single ignition
(Compare diagnostic value with judg-
ment value)
o
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
#1
#6
#3
#2
#5
#4
#1
#6
#3
#2
(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
domg120
EN-02279
Judged as misfire
Threshold value
domg360
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
domg720
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