Subaru Legacy III (2000-2003 year). Manual — part 478

EN(H4DOSTC)-82

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

F: DTC P0103 — MASS OR VOLUME AIR FLOW CIRCUIT HIGH INPUT —

• TROUBLE SYMPTOM:

• Erroneous idling
• Engine stalls.
• Poor driving performance

CAUTION:
After repair or replacement of faulty parts, conduct Clear Memory Mode <Ref. to EN(H4DOSTC)-35,
OPERATION, Clear Memory Mode.> and Inspection Mode <Ref. to EN(H4DOSTC)-33, Inspection
Mode.> .
• WIRING DIAGRAM:

EN-00951

B122

B3

B135

5 6

7 8

2

1

9

4

3

10

24

22

23

25

11 12 13 14 15

26 27 28

16 17 18 19

20 21

BATTERY

E

B122

1

B3

MASS AIR FLOW AND
INTAKE AIR TEMPERATURE

ECM

B135

B :

B84

E :

SBF-5

1 2 3 4 5

3

4

1

2

5

6

1 2 3 4 5 6

B84

B47

2
6

2

4

3

5

E7

B27

E13

B19

E8

1 2 3

8 9 10

4

11 12

13 14 15

16

5 6

7

17

MAIN RELAY

B47

1

2

3

5

4

6

EN(H4DOSTC)-83

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

Step

Value

Yes

No

1

CONNECT SUBARU SELECT MONITOR,
AND READ DATA.
1) Turn the ignition switch to OFF.
2) Connect the Subaru Select Monitor to data

link connector.

3) Turn the ignition switch to ON and Subaru

Select Monitor switch to ON.

4) Start the engine.
5) Read the data of mass air flow sensor sig-

nal using Subaru Select Monitor.
Is the measured value within the specified
value?

NOTE:

For detailed operation procedure, refer to the
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(H4DOSTC)-26, Subaru Select Monitor.>

1.3 g/sec (0.172 lb/min) — 240
g/sec (32 lb/min) or 0.3 — 4.58
V

Even if MI lights
up, the circuit has
returned to a nor-
mal condition at
this time.

Go to step 2.

2

CHECK HARNESS BETWEEN ECM AND
MASS AIR FLOW SENSOR CONNECTOR.
1) Turn the ignition switch to OFF and Subaru

Select Monitor switch to OFF.

2) Disconnect the connector from mass air

flow sensor.

3) Turn the ignition switch to ON and Subaru

Select Monitor switch to ON.

4) Read the data of mass air flow sensor sig-

nal using Subaru Select Monitor.
Does the measured value exceed the spec-
ified value?

NOTE:

For detailed operation procedure, refer to the
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(H4DOSTC)-26, Subaru Select Monitor.>

240 g/sec (32 lb/min) or 4.58 V Repair the battery

short circuit in har-
ness between
mass air flow sen-
sor and ECM con-
nector. After
repair, replace the
ECM.

Replace the mass
air flow sensor.

EN(H4DOSTC)-84

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

G: DTC P0107 — MANIFOLD ABSOLUTE PRESSURE/BAROMETRIC PRES-

SURE CIRCUIT LOW INPUT —

CAUTION:
After repair or replacement of faulty parts, conduct Clear Memory Mode <Ref. to EN(H4DOSTC)-35,
OPERATION, Clear Memory Mode.> and Inspection Mode <Ref. to EN(H4DOSTC)-33, Inspection
Mode.> .
• WIRING DIAGRAM:

EN-00935

B122

PRESSURE SENSOR

THROTTLE BODY

3

2

1

19

9

8

ECM

B135

E21

E2

B21

1
6

20

18

16

1 2 3

B122

B21

E21

1 2 3 4 5 6

1 2

5

6 7

8

13

14 15

16

9 10

11 12

3 4

17 18

19 20

B135

5 6

7 8

2

1

9

4

3

10

24

22

23

25

11 12 13 14 15

26 27 28

16 17 18 19

20 21

EN(H4DOSTC)-85

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

Step

Value

Yes

No

1

CHECK CURRENT DATA.
1) Start the engine.
2) Read the data of intake manifold absolute

pressure signal using Subaru Select Moni-
tor.
Is the measured value less than the speci-
fied value?

NOTE:

For detailed operation procedure, refer to the
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(H4DOSTC)-26, Subaru Select Monitor.>

−

7.2 kPa (

−

54 mmHg,

−

2.1

inHg)

Go to step 3.

Go to step 2.

2

CHECK POOR CONTACT.
Check the poor contact in ECM and pressure
sensor connector.
Is there poor contact in ECM or pressure sen-
sor connector?

There is poor contact.

Repair the poor
contact in ECM or
pressure sensor
connector.

Even if MI lights
up, the circuit has
returned to a nor-
mal condition at
this time.

3

CHECK INPUT SIGNAL FOR ECM.
Measure the voltage between ECM connector
and chassis ground.

Connector & terminal

(B135) No. 9 (+) — Chassis ground (

−−−−

):

Does the measured value exceed the specified
value?

4.5 V

Go to step 5.

Go to step 4.

4

CHECK INPUT SIGNAL FOR ECM.
Measure the voltage between ECM connector
and chassis ground.

Connector & terminal

(B135) No. 9 (+) — Chassis ground (

−−−−

):

Does the measured value change by shaking
harness and connector of ECM while monitor-
ing the value with voltage meter?

The value changes.

Repair the poor
contact in ECM
connector.

Contact SUBARU
distributor service.

NOTE:
Inspection by DTM
is required, be-
cause probable
cause is deteriora-
tion of multiple
parts.

5

CHECK INPUT SIGNAL FOR ECM.
Measure the voltage between ECM and chas-
sis ground.

Connector & terminal

(B135) No. 8 (+) — Chassis ground (

−−−−

):

Is the measured value less than the specified
value?

0.7 V

Go to step 6.

Contact SUBARU
distributor service.

NOTE:
Inspection by DTM
is required, be-
cause probable
cause is deteriora-
tion of multiple
parts.

6

CHECK HARNESS BETWEEN ECM AND
PRESSURE SENSOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from pressure

sensor.

3) Turn the ignition switch to ON.
4) Measure the voltage between pressure

sensor connector and engine ground.

Connector & terminal

(E21) No. 3 (+) — Engine ground (

−−−−

):

Does the measured value exceed the spec-
ified value?

4.5 V

Go to step 7.

Repair the open
circuit in harness
between ECM and
intake manifold
pressure sensor
connector.