Subaru Legacy (2005 year). Manual — part 452

EN(H6DO)(diag)-121

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

Step

Check

Yes

No

1

CHECK OUTPUT SIGNAL FROM ECM.
Measure the voltage between ECM connector
and chassis ground.

Connector & terminal

(B136) No. 16 (+) — Chassis ground (

−

):

Is the voltage more than 4.5 V? Go to step 3.

Go to step 2.

2

CHECK OUTPUT SIGNAL FROM ECM.
Measure the voltage between ECM connector
and chassis ground.

Connector & terminal

(B136) No. 16 (+) — Chassis ground (

−

):

Does the voltage change by
shaking the ECM harness and
connector?

Repair the poor
contact in ECM
connector.

Replace the ECM.
<Ref. to
FU(H6DO)-34,
Engine Control
Module (ECM).>

3

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

Connector & terminal

(B136) No. 22 (+) — Chassis ground (

−

):

Is the voltage more than 4.5 V? Go to step 5.

Go to step 4.

4

CHECK INPUT SIGNAL OF ECM (USING
SUBARU SELECT MONITOR).
Read the data of atmospheric absolute pres-
sure signal using Subaru Select Monitor.

NOTE:

For detailed operation procedure, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(H6DO)(diag)-26, Subaru Select Moni-
tor.>

Is the value more than 13.3
kPa (100 mmHg, 3.94 inHg)
when shaking the ECM har-
ness and connector?

Repair the poor
contact in ECM
connector.

Go to step 5.

5

CHECK HARNESS BETWEEN ECM AND
MANIFOLD ABSOLUTE PRESSURE SEN-
SOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from manifold
absolute pressure sensor.
3) Turn the ignition switch to ON.
4) Measure the voltage between manifold
absolute pressure sensor connector and
engine ground.

Connector & terminal

(E28) No. 3 (+) — Engine ground (

−

):

Is the voltage more than 4.5 V? Go to step 6.

Repair the open
circuit of harness
between ECM and
manifold absolute
pressure sensor
connector.

6

CHECK HARNESS BETWEEN ECM AND
MANIFOLD ABSOLUTE PRESSURE SEN-
SOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance of harness
between ECM and manifold absolute pressure
sensor connector.

Connector & terminal

(B136) No. 22 — (E28) No. 2:

Is the resistance less than 1
Ω?

Go to step 7.

Repair the open
circuit of harness
between ECM and
manifold absolute
pressure sensor
connector.

7

CHECK HARNESS BETWEEN MANIFOLD
ABSOLUTE PRESSURE SENSOR CONNEC-
TOR.
1) Turn the ignition switch to ON.
2) Measure the voltage between ECM con-
nector and chassis ground.

Connector & terminal

(B136) No. 22 (+) — Chassis ground (

−

):

Is the voltage more than 4.5 V? Repair the battery

short of harness
between ECM and
manifold absolute
pressure sensor
connector.

Go to step 8.

EN(H6DO)(diag)-122

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

8

CHECK HARNESS BETWEEN ECM AND
MANIFOLD ABSOLUTE PRESSURE SEN-
SOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Measure the resistance of harness
between ECM and manifold absolute pressure
sensor connector.

Connector & terminal

(B136) No. 35 — (E28) No. 1:

Is the resistance less than 1
Ω?

Go to step 9.

Repair the open
circuit of harness
between ECM and
manifold absolute
pressure sensor
connector.

9

CHECK POOR CONTACT.
Check poor contact in manifold absolute pres-
sure sensor connector.

Is there poor contact in mani-
fold absolute pressure sensor
connector?

Repair the poor
contact in mani-
fold absolute pres-
sure sensor
connector.

Replace the mani-
fold absolute pres-
sure sensor. <Ref.
to FU(H6DO)-23,
Manifold Absolute
Pressure Sensor.>

Step

Check

Yes

No

EN(H6DO)(diag)-123

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

X: DTC P0112 INTAKE AIR TEMPERATURE SENSOR 1 CIRCUIT LOW

DTC DETECTING CONDITION:
Immediately at fault recognition
TROUBLE SYMPTOM:
• Erroneous idling
• Poor driving performance

CAUTION:
After repair or replacement of faulty parts, conduct Clear Memory Mode <Ref. to EN(H6DO)(diag)-41,
OPERATION, Clear Memory Mode.> and Inspection Mode <Ref. to EN(H6DO)(diag)-34, PROCEDURE,
Inspection Mode.>.
WIRING DIAGRAM:

EN-03496

B83

B3

BATTERY

E

B83

1

B3

MASS AIR FLOW AND INTAKE
AIR TEMPERATURE SENSOR

ECM

B136

SBF-7

1 2 3 4 5

3

4

1

2

5

6

B136

B47

*

*

2

4

3

5

31

13

23

35

32

MAIN RELAY

B47

1 2 3 4
5 6 7 8

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

33 34

29

32

30

31

35

6
4

: TERMINAL No.
RANDOM ARRANGEMENT

*

EN(H6DO)(diag)-124

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

Step

Check

Yes

No

1

CHECK CURRENT DATA.
1) Start the engine.
2) Read the data of mass air flow and intake
air temperature sensor signal using Subaru
Select Monitor or general scan tool.

NOTE:

• Subaru Select Monitor
For detailed operation procedure, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(H6DO)(diag)-26, Subaru Select Moni-
tor.>
• General scan tool
For detailed operation procedure, refer to the
general scan tool operation manual.

Is the intake air temperature
more than 120

°C (248°F)?

Go to step 2.

Repair the poor
contact.

NOTE:
In this case, repair
the following:
• Poor contact in
mass air flow and
intake air tempera-
ture sensor
• Poor contact in
ECM
• Poor contact in
coupling connector
• Poor contact in
joint connector

2

CHECK HARNESS BETWEEN MASS AIR
FLOW AND INTAKE AIR TEMPERATURE
SENSOR AND ECM CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from mass air
flow and intake air temperature sensor.
3) Turn the ignition switch to ON.
4) Read the data of mass air flow and intake
air temperature sensor signal using Subaru
Select Monitor or general scan tool.

NOTE:

• Subaru Select Monitor
For detailed operation procedure, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(H6DO)(diag)-26, Subaru Select Moni-
tor.>
• General scan tool
For detailed operation procedure, refer to the
general scan tool operation manual.

Is the intake air temperature
less than

−40°C (−40°F)?

Replace the mass
air flow and intake
air temperature
sensor. <Ref. to
FU(H6DO)-24,
Mass Air Flow and
Intake Air Temper-
ature Sensor.>

Repair the ground
short circuit of har-
ness between
mass air flow and
intake air tempera-
ture sensor and
ECM connector.