Subaru Legacy (2005 year). Service manual — part 463

EN(H6DO)(diag)-165

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

AQ:DTC P0171 SYSTEM TOO LEAN (BANK 1)

Refer to DTC P0175 for diagnostic procedure. <Ref. to EN(H6DO)(diag)-166, DTC P0175 SYSTEM TOO
RICH (BANK 2), Diagnostic Procedure with Diagnostic Trouble Code (DTC).>

AR:DTC P0172 SYSTEM TOO RICH (BANK 1)

Refer to DTC P0175 for diagnostic procedure. <Ref. to EN(H6DO)(diag)-166, DTC P0175 SYSTEM TOO
RICH (BANK 2), Diagnostic Procedure with Diagnostic Trouble Code (DTC).>

AS:DTC P0174 SYSTEM TOO LEAN (BANK 2)

Refer to DTC P0175 for diagnostic procedure. <Ref. to EN(H6DO)(diag)-166, DTC P0175 SYSTEM TOO
RICH (BANK 2), Diagnostic Procedure with Diagnostic Trouble Code (DTC).>

5

CHECK EXHAUST SYSTEM.
Check exhaust system parts.

NOTE:

Check the following items.
• Loose part and incomplete installation of
exhaust system
• Damage (crack, hole etc.) of parts
• Looseness and ill fitting of parts between
front oxygen (A/F) sensor and rear oxygen
sensor

Is there any fault in exhaust
system?

Repair or replace
faulty parts.

Replace the rear
oxygen sensor.
<Ref. to
FU(H6DO)-32,
Rear Oxygen Sen-
sor.>

Step

Check

Yes

No

EN(H6DO)(diag)-166

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

AT:DTC P0175 SYSTEM TOO RICH (BANK 2)

DTC DETECTING CONDITION:
Detects when malfunction occurs in 2 continuous driving cycles.
TROUBLE SYMPTOM:
• Erroneous idling
• Engine stalls.
• 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.>.

Step

Check

Yes

No

1

CHECK EXHAUST SYSTEM.

Are there holes or loose bolts
on exhaust system?

Repair the exhaust
system.

Go to step 2.

2

CHECK AIR INTAKE SYSTEM.

Are there holes, loose bolts or
disconnection of hose on air
intake system?

Repair the air
intake system.

Go to step 3.

3

CHECK EGR VALVE.

Is the EGR valve stuck?

Replace the EGR
valve.

Go to step 4.

4

CHECK PURGE CONTROL SOLENOID
VALVE.

Is the purge control solenoid
valve stuck?

Replace the purge
control solenoid
valve.

Go to step 5.

5

CHECK PCV VALVE.

Is the PCV valve stuck?

Replace the PCV
valve.

Go to step 6.

6

CHECK FUEL PRESSURE.

Warning:

• Place “NO FIRE” signs near the working
area.
• Be careful not to spill fuel.

1) Release the fuel pressure.

(1) Disconnect the connector from fuel
pump relay.
(2) Start the engine and run until it stalls.
(3) After the engine stalls, crank it for five
more seconds.
(4) Turn the ignition switch to OFF.

2) Connect the connector to fuel pump relay.
3) Disconnect the fuel delivery hose, and con-
nect the fuel pressure gauge.
4) Install the fuel filler cap.
5) Start the engine and idle while gear posi-
tion is neutral.
6) Measure the fuel pressure while discon-
necting pressure regulator vacuum hose from
intake manifold.

Warning:

Release fuel pressure before removing the
fuel pressure gauge.

NOTE:

If fuel pressure does not increase, squeeze fuel
return hose 2 to 3 times, then measure fuel
pressure again.

Is fuel pressure 333 — 363

kPa (3.4 — 3.7 kgf/cm

2

, 48 —

53 psi)?

Go to step 7.

Repair the follow-
ing items.
Fuel pressure is
too high:

• Clogged fuel
return line or
bent hose

Fuel pressure is
too low:

• Improper fuel
pump discharge
• Clogged fuel
supply line

EN(H6DO)(diag)-167

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

7

CHECK FUEL PRESSURE.
After connecting the pressure regulator vac-
uum hose, measure fuel pressure.

Warning:

Release fuel pressure before removing the
fuel pressure gauge.

NOTE:

• If fuel pressure does not increase, squeeze
fuel return hose 2 to 3 times, then measure
fuel pressure again.
• If the measured value at this step is out of
specifications, check or replace pressure regu-
lator and pressure regulator vacuum hose.

Is fuel pressure 279 — 309

kPa (2.85 — 3.15 kgf/cm

2

, 40

— 45 psi)?

Go to step 8.

Repair the follow-
ing items.
Fuel pressure is
too high:

• Faulty pres-
sure regulator
• Clogged fuel
return line or
bent hose

Fuel pressure is
too low:

• Faulty pres-
sure regulator
• Improper fuel
pump discharge
• Clogged fuel
supply line

8

CHECK ENGINE COOLANT TEMPERATURE
SENSOR.
1) Start the engine and warm-up completely.
2) Read the data of engine coolant tempera-
ture 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 engine coolant tempera-
ture 70 — 100

°C (158 —

212

°F)?

Go to step 9.

Replace the
engine coolant
temperature sen-
sor. <Ref. to
FU(H6DO)-18,
Engine Coolant
Temperature Sen-
sor.>

9

CHECK MANIFOLD PRESSURE SENSOR
SIGNAL.
1) Start and warm-up the engine until engine
coolant temperature is above 60

°C (140°F).

2) Place the select lever in “N” or “P” position.
3) Turn the A/C switch to OFF.
4) Turn all the accessory switches to OFF.
5) Read the data of manifold absolute pres-
sure sensor signal using Subaru Select Moni-
tor 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 measurement value 24.0
— 41.3 kPa (180 — 310
mmHg, 7.09 — 12.20 inHg)
when idling and 73.3 — 106.6
kPa (550 — 800 mmHg, 21.65
— 31.50 inHg) when the igni-
tion turns to ON?

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

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

Step

Check

Yes

No

EN(H6DO)(diag)-168

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

AU:DTC P0197 ENGINE OIL TEMPERATURE SENSOR LOW

DTC DETECTING CONDITION:
Immediately at fault recognition
TROUBLE SYMPTOM:
• Hard to start
• 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-03500

E75

E2

B21

B136

ECM

B83

1

19

35

E1

B20

2

3

27

*

: TERMINAL No.
RANDOM ARRANGEMENT

*

*

E75

1 2

B20

1 2 3 4
5 6 7 8
9 10 11 12

13 14 15 16

B21

1 2 3 4

12 13 14 15

5 6 7 8

16 17 18 19

9 10 11

20 21 22

23 24 25 26 27 28 29 30 31 32 33

35

34

37

36

39

38

41

40

43

42

44

45

47

46

49

48

51

50

53

52

54

B136

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

1 2 3 4
5 6 7 8

B83

OIL

TEMPERATURE

SENSOR