Subaru Impreza 3 / Impreza WRX / Impreza WRX STI. Manual — part 257

EN(H4DOTC)(diag)-252

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

3

CHECK WAVEFORM DATA ON THE SUBA-
RU SELECT MONITOR (WHILE IDLING).
1) Run the engine at idle.
2) In the condition of step 1), use the Subaru
Select Monitor to read the waveform data.
• At normal condition

• At abnormal condition 1 (numerous inver-
sion)

• At abnormal condition 2 (noise input)

Is a normal waveform dis-
played?

Go to step

4.

• The waveform is
displayed at abnor-
mal condition 1: Go
to step

4.

• The waveform is
displayed at abnor-
mal condition 2: Go
to step

5.

4

CHECK CATALYTIC CONVERTER.

Is the catalytic converter dam-
aged?

Replace the cata-
lytic converter.
<Ref. to EC(STI)-
5, Front Catalytic
Converter.> <Ref.
to EC(w/o STI)-5,
Front Catalytic
Converter.>

Go to step

5.

5

CHECK REAR OXYGEN SENSOR CONNEC-
TOR AND COUPLING CONNECTOR.

Has water entered the connec-
tor?

Completely
remove any water
inside.

Go to step

6.

Step

Check

Yes

No

EN-06668

1

0

10 sec/div

REAR OXYGEN

SENSOR VOLTAGE

(V)

EN-06669

1

0

10 sec/div

REAR OXYGEN

SENSOR VOLTAGE

(V)

EN-06670

1

0

10 sec/div

REAR OXYGEN

SENSOR VOLTAGE

(V)

EN(H4DOTC)(diag)-253

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

6

CHECK HARNESS BETWEEN ECM AND
REAR OXYGEN SENSOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM and
rear oxygen sensor.
3) Measure the resistance of harness between
ECM connector and rear oxygen sensor con-
nector.

Connector & terminal

(B136) No. 20 — (T6) No. 3:
(B135) No. 30 — (T6) No. 4:

Is the resistance less than 1 Ω? Go to step

7.

Repair the harness
and connector.
NOTE:

Repair the follow-
ing locations.
• Open circuit in
harness between
ECM

connector

and rear oxygen
sensor connector
• Poor contact of
coupling connector

7

CHECK REAR OXYGEN SENSOR SHIELD.
1) Turn the ignition switch to OFF.
2) Expose the rear oxygen sensor connector
body side harness sensor shield.
3) Measure the resistance between sensor
shield and chassis ground.

Is the resistance less than 1 Ω? Go to step

8.

Repair the open
circuit of rear oxy-
gen sensor har-
ness.

8

CHECK ENGINE OIL AMOUNT AND EX-
HAUST GAS.
1) Check the engine oil amount. <Ref. to
LU(STI)-11, INSPECTION, Engine Oil.>
2) Check exhaust gas during idling.

Does the engine oil amount
drop or white smoke emit from
the muffler?

Check the engine,
and repair the
defective part.
<Ref. to ME(STI)-
107, INSPEC-
TION, Engine
Trouble in Gen-
eral.> <Ref. to
ME(w/o STI)-103,
INSPECTION,
Engine Trouble in
General.>
After repairing the
engine, replace the
catalytic con-
verter. <Ref. to
EX(STI)-8, Center
Exhaust Pipe.>
After the catalytic
converter is
replaced, perform
step 2 to check the
normal waveform
is displayed, and
then exit the proce-
dure.

Go to step

9.

9

CHECK IGNITION SYSTEM.
1) Check the spark plug. <Ref. to IG(STI)-5,
INSPECTION, Spark Plug.> <Ref. to IG(w/o
STI)-6, INSPECTION, Spark Plug.>
2) Check the status of the ignition coil connec-
tor and the spark plug terminal.

Is there any fault in the ignition
system?

After repairing the
ignition system,
replace the cata-
lytic converter.
<Ref. to EX(STI)-8,
Center Exhaust
Pipe.>
After the catalytic
converter is
replaced, perform
step 2 to check the
normal waveform
is displayed, and
then exit the proce-
dure.

Go to step

10.

Step

Check

Yes

No

EN(H4DOTC)(diag)-254

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

10

CHECK FUEL SYSTEM.
1) Refer to and check the items in “Insufficient
fuel supply to fuel injector (except for “a. Fuel
pump does not operate.”)” and “Leakage or
blow out of fuel”. <Ref. to FU(STI)-98, INSPEC-
TION, Fuel System Trouble in General.> <Ref.
to FU(w/o STI)-94, INSPECTION, Fuel System
Trouble in General.>
2) Check throttle body. <Ref. to FU(STI)-15,
INSPECTION, Throttle Body.> <Ref. to FU(w/o
STI)-16, INSPECTION, Throttle Body.>
3) Check intake manifold. <Ref. to FU(STI)-33,
INSPECTION, Intake Manifold.> <Ref. to FU(w/
o STI)-33, INSPECTION, Intake Manifold.>

Is there any fault in the fuel sys-
tem?

After repairing the
fuel system,
replace the cata-
lytic converter.
<Ref. to EX(STI)-8,
Center Exhaust
Pipe.>
After the catalytic
converter is
replaced, perform
step 2 to check the
normal waveform
is displayed, and
then exit the proce-
dure.

Go to step

11.

11

CHECK DTC.

Is any other DTC displayed?

Check the appropri-
ate DTC using the
“List of Diagnostic
Trouble Code
(DTC)”. <Ref. to
EN(H4DOTC)(diag)
-87, List of Diagnos-
tic Trouble Code
(DTC).>
After checking the
DTC, replace the
catalytic con-
verter. <Ref. to
EX(STI)-8, Center
Exhaust Pipe.>
After the catalytic
converter is
replaced, perform
step 2 to check the
normal waveform
is displayed, and
then exit the proce-
dure.

Replace the rear
oxygen sensor.
<Ref. to FU(STI)-
56, Rear Oxygen
Sensor.> <Ref. to
FU(w/o STI)-55,
Rear Oxygen Sen-
sor.>

Step

Check

Yes

No

EN(H4DOTC)(diag)-255

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

CG:DTC P0441 EVAPORATIVE EMISSION CONT. SYS. INCORRECT PURGE

FLOW

DTC DETECTING CONDITION:

• Detected when two consecutive driving cycles with fault occur.

• GENERAL DESCRIPTION <Ref. to GD(H4DOTC)-152, DTC P0441 EVAPORATIVE EMISSION CONT.

SYS. INCORRECT PURGE FLOW, Diagnostic Trouble Code (DTC) Detecting Criteria.>

TROUBLE SYMPTOM:

Improper idling
CAUTION:

After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(H4DOTC)(diag)-63,

OPERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(H4DOTC)(diag)-49, PROCE-

DURE, Inspection Mode.>.

Step

Check

Yes

No

1

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

Check the appropri-
ate DTC using the
“List of Diagnostic
Trouble Code
(DTC)”. <Ref. to
EN(H4DOTC)(diag)
-87, List of Diagnos-
tic Trouble Code
(DTC).>

Go to step

2.

2

CHECK PURGE CONTROL SOLENOID
VALVE.
Operate the purge control solenoid valve using
the Subaru Select Monitor.
NOTE:

Refer to “Compulsory Valve Operation Check
Mode” for more operation procedures. <Ref. to
EN(H4DOTC)(diag)-64, Compulsory Valve Op-
eration Check Mode.>

Does the purge control sole-
noid valve operate?

Go to step

3.

Replace the purge
control solenoid
valve. <Ref. to
EC(STI)-11, Purge
Control Solenoid
Valve.> <Ref. to
EC(w/o STI)-11,
Purge Control
Solenoid Valve.>

3

CHECK EVAPORATIVE EMISSION CON-
TROL SYSTEM LINE.
1) Turn the ignition switch to OFF.
2) Check the delivery (test) mode connector is
disconnected.

Are there holes, cracks, clog-
ging, or disconnection, miscon-
nection of hoses or pipes in
evaporative emission control
system?

Repair or replace
the hoses or pipes.

Repair the poor
contact of ECM
connector.