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Subaru Legacy III (2000-2003 year). Manual - part 138

EN(H4SO)-164

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

AB:DTC P0172 — SYSTEM TOO RICH (BANK 1) —

• 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(H4SO)-47, OPER-
ATION, Clear Memory Mode.> and Inspection Mode <Ref. to EN(H4SO)-40, OPERATION, Inspection
Mode.> .

Step

Value

Yes

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

DTC indicated.

Inspect the rele-
vant DTC using
“List of Diagnostic
Trouble Code
(DTC)”. <Ref. to
EN(H4SO)-83, List
of Diagnostic
Trouble Code
(DTC).>

Go to step 2.

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

There are holes or loose bolts
on exhaust system.

Repair exhaust
system.

Go to step 3.

CHECK EGR VALVE.
Is EGR valve clogged?

EGR valve is clogged.

Replace EGR
valve.

Go to step 4.

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

There are holes, loose bolts or
disconnection of hose on air
intake system.

Repair air intake
system.

Go to step 5.

CHECK PURGE CONTROL SOLENOID
VALVE.
Is purge control solenoid valve clogged?

Purge control solenoid valve is
clogged.

Replace purge
control solenoid
valve.

Go to step 6.

CHECK PCV VALVE.
Is PCV valve clogged?

PCV valve is clogged.

Replace PCV
valve.

Go to step 7.

EN(H4SO)-165

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

CHECK FUEL PRESSURE.

Warning:

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

1) Release 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, re-
lease 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/

, 41 — 46 psi)

Go to step 8.

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
supply line

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, re-
lease 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/

, 30 — 34 psi)

Go to step 9.

Repair the follow-
ing items.
Fuel pressure too
high

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

Fuel pressure too
low

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

Step

Value

Yes

EN(H4SO)-166

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

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.
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(H4SO)-32, Subaru Select Moni-
tor.>
•OBD-II general scan tool
For detailed operation procedures, refer to the
OBD-II General Scan Tool Instruction Manual.

70 - 100

C (158 - 212

Go to step 10.

Replace engine
coolant tempera-
ture sensor. <Ref.
to FU(H4SO)-26,
Engine Coolant
Temperature Sen-
sor.>

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

coolant temperature is greater than 60

(140

F).

2) Place the selector lever in “N” or “P” posi-

tion.

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:

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

Contact SUBARU
distributor service.

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

Replace intake air
temperature and
pressure sensor.
<Ref. to
FU(H4SO)-32,
Pressure Sensor.>

Step

Value

Yes

EN(H4SO)-167

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

AC:DTC P0301 — CYLINDER 1 MISFIRE DETECTED —

NOTE:
For the diagnostic procedure, refer to DTC P0304. <Ref. to EN(H4SO)-168, DTC P0304 — CYLINDER 4
MISFIRE DETECTED —, Diagnostic Procedure with Diagnostic Trouble Code (DTC).>

AD:DTC P0302 — CYLINDER 2 MISFIRE DETECTED —

NOTE:
For the diagnostic procedure, refer to DTC P0304. <Ref. to EN(H4SO)-168, DTC P0304 — CYLINDER 4
MISFIRE DETECTED —, Diagnostic Procedure with Diagnostic Trouble Code (DTC).>

AE:DTC P0303 — CYLINDER 3 MISFIRE DETECTED —

NOTE:
For the diagnostic procedure, refer to DTC P0304. <Ref. to EN(H4SO)-168, DTC P0304 — CYLINDER 4
MISFIRE DETECTED —, Diagnostic Procedure with Diagnostic Trouble Code (DTC).>

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