Subaru Legacy III (2000-2003 year). Manual - part 347

EN(H6DO)-190

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

9

CHECK INTAKE MANIFOLD PRESSURE 
SENSOR.
1) Start the engine and warm-up engine until 

coolant temperature is greater than 75

°

C 

(167

°

F).

2) Place the shift lever in neutral position.
3) Turn A/C switch to OFF.
4) Turn all accessory switches to OFF.
5) Read data of intake manifold pressure sen-

sor signal using Subaru Select Monitor or 
OBD-II general scan tool.
Is the measured value within the specified 
range?

NOTE:

• Subaru Select Monitor
For detailed operation procedure, refer to the 
“READ CURRENT DATA FOR ENGINE”. 
<Ref. to EN(H6DO)-34, Subaru Select Moni-
tor.>
• OBD-II general scan tool
For detailed operation procedure, refer to the 
OBD-II General Scan Tool Instruction Manual.

Ignition ON 73.3 — 106.6 kPa 
(550 — 800 mmHg, 21.65 — 
31.50 inHg), Idling  24.0 — 
41.3 kPa (180 — 310 mmHg, 
7.09 — 12.20 inHg)

Go to step 10.

Replace intake 
manifold pressure 
sensor. <Ref. to 
FU(H6DO)-34, 
Intake Manifold 
Pressure Sensor.>

10

CHECK INTAKE AIR TEMPERATURE SEN-
SOR.
1) Start the engine and warm-up engine until 

coolant temperature is greater than 75

°

C 

(167

°

F).

2) Place the shift lever in neutral position.
3) Turn A/C switch to OFF.
4) Turn all accessory switches to OFF.
5) Open front hood.
6) Measure ambient temperature.
7) Read data of intake manifold pressure sen-

sor signal using Subaru Select Monitor or 
OBD-II general scan tool.
Is value within the specified range when 
ambient temperature is subtracted from 
intake air temperature greater than 

−

10

°

C 

(14

°

F) and less than 50

°

C (122

°

F)?

NOTE:

• Subaru Select Monitor
For detailed operation procedure, refer to the 
“READ CURRENT DATA FOR ENGINE”. 
<Ref. to EN(H6DO)-34, Subaru Select Moni-
tor.>
• OBD-II general scan tool
For detailed operation procedure, refer to the 
OBD-II General Scan Tool Instruction Manual.

 

−

10 — 50

°

C (14 — 122

°

F)

Contact SUBARU 
distributor service.

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

Check intake air 
temperature sen-
sor. <Ref. to 
FU(H6DO)-35, 
Intake Air Temper-
ature Sensor.>

Step

Value

Yes

No

EN(H6DO)-191

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

AG:DTC P0174 — SYSTEM TOO LEAN (BANK 2) —

NOTE:
For the diagnostic procedure, refer to DTC P0175. <Ref. to EN(H6DO)-192, DTC P0175 — SYSTEM TOO
RICH (BANK 2) —, Diagnostic Procedure with Diagnostic Trouble Code (DTC).>

EN(H6DO)-192

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

AH:DTC P0175 — SYSTEM TOO RICH (BANK 2) —

• DTC DETECTING CONDITION:

• Two consecutive driving cycles with fault

• 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)-54, OP-
ERATION, Clear Memory Mode.> and Inspection Mode <Ref. to EN(H6DO)-47, OPERATION, Inspec-
tion Mode.>.

Step

Value

Yes

No

1

CHECK ANY OTHER DTC ON DISPLAY.
Is any other DTC displayed?

Another DTC is displayed.

Inspect the rele-
vant DTC using 
“List of Diagnostic 
Trouble Code 
(DTC)”. <Ref. to 
EN(H6DO)-89, List 
of Diagnostic 
Trouble Code 
(DTC).>

Go to step 2.

2

CHECK EXHAUST SYSTEM.
Are there holes or loose bolts on exhaust sys-
tem?

Holes or loose bolts are found. Repair exhaust 

system.

Go to step 3.

3

CHECK AIR INTAKE SYSTEM.
Are there holes, loose bolts or disconnection of 
hose on air intake system?

Holes, loose bolts or discon-
nection of hose is found.

Repair air intake 
system.

Go to step 4.

4

CHECK FUEL PRESSURE.

Warning:

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

1) Lower fuel pressure.

(1) Disconnect connector from fuel pump 

relay.

(2) Start the engine and run it until it stalls.
(3) After the engine stalls, crank it for five 

more seconds.

(4) Turn ignition switch to OFF.

2) Connect connector to fuel pump relay.
3) Disconnect fuel delivery hose from fuel fil-

ter, and connect fuel pressure gauge.

4) Install fuel filler cap.
5) Start the engine and idle while gear position 

is neutral.

6) Measure fuel pressure while disconnecting 

pressure regulator vacuum hose from 
intake manifold.
Is the measured value within the specified 
range?

Warning:

Before removing fuel pressure gauge, lower
fuel pressure.

NOTE:

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

284 — 314 kPa (2.9 — 3.2 kg/

cm

2

, 41 — 46 psi)

Go to step 5.

Repair the follow-
ing items.

Fuel pressure too 

high

• Clogged fuel 
return line or bent 
hose

Fuel pressure too 

low

• Improper fuel 
pump discharge
• Clogged fuel sup-
ply line

EN(H6DO)-193

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

5

CHECK FUEL PRESSURE.
After connecting pressure regulator vacuum 
hose, measure fuel pressure.
Is the measured value within the specified 
range?

Warning:

Before removing fuel pressure gauge, lower
fuel pressure.

NOTE:

• If fuel pressure does not increase, squeeze 
fuel return hose 2 to 3 times, then measure 
fuel pressure again.
• If out of specification as measured at this 
step, check or replace pressure regulator and 
pressure regulator vacuum hose.

206 — 235 kPa (2.1 — 2.4 kg/

cm

2

, 30 — 34 psi)

Go to step 6.

Repair the follow-
ing items.

Fuel pressure too 

high

• Faulty pressure 
regulator
• Clogged fuel 
return line or bent 
hose

Fuel pressure too 

low

• Faulty pressure 
regulator
• Improper fuel 
pump discharge
• Clogged fuel sup-
ply line

6

CHECK FUEL INJECTOR.
1) Turn ignition switch to OFF.
2) Remove left bank fuel injector. <Ref. to 

FU(H6DO)-39, REMOVAL, Fuel Injector.>

3) Check fuel injector.

Is fuel injector clogged? 

Fuel injector is clogged.

Replace fuel injec-
tor. <Ref. to 
FU(H6DO)-39, 
Fuel Injector.> 

Go to step 7.

7

CHECK FUEL INJECTOR.
Measure resistance between terminals of fuel 
injector.

Terminals

No. 1 — No. 2

Is the measured value within the specified 
range?

5 — 20 

Ω

Go to step 8.

Replace fuel injec-
tor. <Ref. to 
FU(H6DO)-39, 
Fuel Injector.>

8

CHECK ENGINE COOLANT TEMPERATURE 
SENSOR.
1) Start the engine and warm-up completely.
2) Read data of engine coolant temperature 

sensor signal using Subaru Select Monitor 
or OBD-II general scan tool.
Does the measured value exceed the spec-
ified value?

NOTE:

• Subaru Select Monitor
For detailed operation procedure, refer to the 
“READ CURRENT DATA FOR ENGINE”. 
<Ref. to EN(H6DO)-34, Subaru Select Moni-
tor.>
• OBD-II general scan tool
For detailed operation procedures, refer to the 
OBD-II General Scan Tool Instruction Manual.

75

°

C (167

°

F)

Go to step 9.

Replace engine 
coolant tempera-
ture sensor. <Ref. 
to FU(H6DO)-29, 
Engine Coolant 
Temperature Sen-
sor.>

Step

Value

Yes

No