
EN(H6DO)(diag)-331
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1CHECK ANY OTHER DTC ON DISPLAY.Is any other DTC displayed? Inspect the rele-
vant DTC using
“List of Diagnostic
Tr o u b l e C o d e
(DTC)”.
69, List of Diag-
nostic Trouble
Code (DTC).>
Go to step 2.
2CHECK FRONT OXYGEN (A/F) SENSOR DA-
TA.
1) Start the engine.
2) While observing the Subaru Select Monitor
or general scan tool screen, warm-up the
engine until engine coolant temperature is
above 75°C (167°F).
If the engine is already warmed-up, operate at
idle speed for at least 1 minute.
3) Read data of front oxygen (A/F) sensor sig-
nal using the Subaru Select Monitor or general
scan tool.
NOTE:
•Subaru Select Monitor
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”.
tor.>
•General scan tool
For detailed operation procedure, refer to the
general scan tool operation manual.
Is the measured value within
0.86 — 1.15 at idle?
Go to step 3.Go to step 4.
3CHECK REAR OXYGEN SENSOR SIGNAL.
1) Race engine at speeds from idling to 5,000
rpm for a total of 5 cycles.
NOTE:To increase engine speed to 5,000 rpm, slowly
depress accelerator pedal, taking approximate-
ly 5 seconds, and quickly release accelerator
pedal to decrease engine speed.
2) Operate the LED operation mode for
engine.
NOTE:•Subaru Select Monitor
For detailed operation procedure, refer to the
“LED OPERATION MODE FOR ENGINE”.
Does the LED of {Rear O2
Rich Signal} blink?
Check front oxy-
gen (A/F) sensor
circuit.
Check rear oxygen
sensor circuit.
Rear Oxygen Sen-
sor.>
4 CHECK EXHAUST SYSTEM.
Check exhaust system parts.
NOTE:Check the following items.
•Looseness of part installation
•Damage (crack, hole etc.) of parts
•Looseness of the front oxygen (A/F) sensor
•Looseness or 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 par ts.
Go to step 5.
5CHECK AIR INTAKE SYSTEM.Are there holes, loose bolts or
disconnection of hose on air
intake system?
Repair the air
intake system.
Go to step 6.

EN(H6DO)(diag)-339
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1CHECK ANY OTHER DTC ON DISPLAY.Is any other DTC displayed? Inspect the rele-
vant DTC using
“List of Diagnostic
Tr o u b l e C o d e
(DTC)”.
69, List of Diag-
nostic Trouble
Code (DTC).>
Go to step 2.
2CHECK FRONT OXYGEN (A/F) SENSOR DA-
TA.
1) Start the engine.
2) While observing the Subaru Select Monitor
or general scan tool screen, warm-up the
engine until engine coolant temperature is
above 75°C (167°F).
If the engine is already warmed-up, operate at
idle speed for at least 1 minute.
3) Read data of front oxygen (A/F) sensor sig-
nal using the Subaru Select Monitor or general
scan tool.
NOTE:
•Subaru Select Monitor
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”.
tor.>
•General scan tool
For detailed operation procedure, refer to the
general scan tool operation manual.
Is the measured value within
0.86 — 1.15 at idle?
Go to step 3.Go to step 4.
3CHECK REAR OXYGEN SENSOR SIGNAL.
1) Race engine at speeds from idling to 5,000
rpm for a total of 5 cycles.
NOTE:To increase engine speed to 5,000 rpm, slowly
depress accelerator pedal, taking approximate-
ly 5 seconds, and quickly release accelerator
pedal to decrease engine speed.
2) Operate the LED operation mode for
engine.
NOTE:•Subaru Select Monitor
For detailed operation procedure, refer to the
“LED OPERATION MODE FOR ENGINE”.
Does the LED of {Rear O2
Rich Signal} blink?
Check front oxy-
gen (A/F) sensor
circuit.
Check rear oxygen
sensor circuit.
Rear Oxygen Sen-
sor.>
4 CHECK EXHAUST SYSTEM.
Check exhaust system parts.
NOTE:Check the following items.
•Looseness of part installation
•Damage (crack, hole etc.) of parts
•Looseness of the front oxygen (A/F) sensor
•Looseness or 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 par ts.
Go to step 5.
5CHECK AIR INTAKE SYSTEM.Are there holes, loose bolts or
disconnection of hose on air
intake system?
Repair the air
intake system.
Go to step 6.

EN(H6DO)(diag)-347
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1CHECK ANY OTHER DTC ON DISPLAY.Is any other DTC displayed? Inspect the rele-
vant DTC using
“List of Diagnostic
Tr o u b l e C o d e
(DTC)”.
69, List of Diag-
nostic Trouble
Code (DTC).>
Go to step 2.
2CHECK FRONT OXYGEN (A/F) SENSOR DA-
TA.
1) Start the engine.
2) While observing the Subaru Select Monitor
or general scan tool screen, warm-up the
engine until engine coolant temperature is
above 75°C (167°F).
If the engine is already warmed-up, operate at
idle speed for at least 1 minute.
3) Read data of front oxygen (A/F) sensor sig-
nal using the Subaru Select Monitor or general
scan tool.
NOTE:
•Subaru Select Monitor
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”.
tor.>
•General scan tool
For detailed operation procedure, refer to the
general scan tool operation manual.
Is the measured value within
0.86 — 1.15 at idle?
Go to step 3.Go to step 4.
3CHECK REAR OXYGEN SENSOR SIGNAL.
1) Race engine at speeds from idling to 5,000
rpm for a total of 5 cycles.
NOTE:To increase engine speed to 5,000 rpm, slowly
depress accelerator pedal, taking approximate-
ly 5 seconds, and quickly release accelerator
pedal to decrease engine speed.
2) Operate the LED operation mode for
engine.
NOTE:•Subaru Select Monitor
For detailed operation procedure, refer to the
“LED OPERATION MODE FOR ENGINE.”.
Does the LED of {Rear O2
Rich Signal} blink?
Check front oxy-
gen (A/F) sensor
circuit.
Check rear oxygen
sensor circuit.
Rear Oxygen Sen-
sor.>
4 CHECK EXHAUST SYSTEM.
Check exhaust system parts.
NOTE:Check the following items.
•Looseness of part installation
•Damage (crack, hole etc.) of parts
•Looseness of the front oxygen (A/F) sensor
•Looseness or 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 par ts.
Go to step 5.
5CHECK AIR INTAKE SYSTEM.Are there holes, loose bolts or
disconnection of hose on air
intake system?
Repair the air
intake system.
Go to step 6.

EN(H6DO)(diag)-355
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1CHECK ANY OTHER DTC ON DISPLAY.Is any other DTC displayed? Inspect the rele-
vant DTC using
“List of Diagnostic
Tr o u b l e C o d e
(DTC)”.
69, List of Diag-
nostic Trouble
Code (DTC).>
Go to step 2.
2CHECK FRONT OXYGEN (A/F) SENSOR DA-
TA.
1) Start the engine.
2) While observing the Subaru Select Monitor
or general scan tool screen, warm-up the
engine until engine coolant temperature is
above 75°C (167°F).
If the engine is already warmed-up, operate at
idle speed for at least 1 minute.
3) Read data of front oxygen (A/F) sensor sig-
nal using the Subaru Select Monitor or general
scan tool.
NOTE:
•Subaru Select Monitor
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”.
tor.>
•General scan tool
For detailed operation procedure, refer to the
general scan tool operation manual.
Is the measured value within
0.86 — 1.15 at idle?
Go to step 3.Go to step 4.
3CHECK REAR OXYGEN SENSOR SIGNAL.
1) Race engine at speeds from idling to 5,000
rpm for a total of 5 cycles.
NOTE:To increase engine speed to 5,000 rpm, slowly
depress accelerator pedal, taking approximate-
ly 5 seconds, and quickly release accelerator
pedal to decrease engine speed.
2) Operate the LED operation mode for
engine.
NOTE:•Subaru Select Monitor
For detailed operation procedure, refer to the
“LED OPERATION MODE FOR ENGINE.”.
Does the LED of {Rear O2
Rich Signal} blink?
Check front oxy-
gen (A/F) sensor
circuit.
Check rear oxygen
sensor circuit.
Rear Oxygen Sen-
sor.>
4 CHECK EXHAUST SYSTEM.
Check exhaust system parts.
NOTE:Check the following items.
•Looseness of part installation
•Damage (crack, hole etc.) of parts
•Looseness of the front oxygen (A/F) sensor
•Looseness or 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 par ts.
Go to step 5.
5CHECK AIR INTAKE SYSTEM.Are there holes, loose bolts or
disconnection of hose on air
intake system?
Repair the air
intake system.
Go to step 6.

EN(H6DO)(diag)-393
General Diagnostic Table
ENGINE (DIAGNOSTICS)
*1: Check ignition coil & ignitor assembly and spark plug.
*2: Indicate the symptom occurring only in cold temperatures.
*3: Make sure the secure installation.
*4: Check the fuel injector and fuel pressure regulator.
*5: Inspect air leak in air intake system.
6. Surging
1) Mass air flow and intake air temperature sensor
2) Manifold absolute pressure sensor
3) Engine coolant temperature sensor (*2)
4) Crankshaft position sensor (*3)
5) Camshaft position sensor (*3)
6) Fuel injection parts (*4)
7) Electronic throttle control
8) Fuel pump and fuel pump relay
7. Spark knock
1) Mass air flow and intake air temperature sensor
2) Manifold absolute pressure sensor
3) Engine coolant temperature sensor
4) Knock sensor
5) Fuel injection parts (*4)
6) Fuel pump and fuel pump relay
8. After burning in exhaust system
1) Mass air flow and intake air temperature sensor
2) Manifold absolute pressure sensor
3) Engine coolant temperature sensor (*2)
4) Fuel injection parts (*4)
5) Fuel pump and fuel pump relay
Symptom Problem parts

EX(H6DO)-2
General Description
EXHAUST
1. General Description
A: COMPONENT
EX-02129
T2
T4
T5
T1
T1
T3
T3
T4
T4
(18)
(12)
(11)
(10)
(8)
T6
T6
(20)
(21)
(22)
(23)
(25)
(24)
(17)(24)
(24)
(24)
(26)(24)
(25)
(16)
(26)
(13)
(15)
(19)
(14)
T3
(6)
(7)(5)
T3
(4)
(3)
(1)
(2)
(9)

EX(H6DO)-3
General Description
EXHAUST
B: CAUTION
•Wear work clothing, including a cap, protective
goggles and protective shoes during operation.
•Remove contamination including dirt and corro-
sion before removal, installation or disassembly.
•Keep the disassembled parts in order and pro-
tect them from dust and dirt.
•Before removal, installation or disassembly, be
sure to clarify the failure. Avoid unnecessary re-
moval, installation, disassembly and replacement.
•Be careful not to burn yourself, because each
part on the vehicle is hot after running.
•Be sure to tighten fasteners including bolts and
nuts to the specified torque.
•Place shop jacks or rigid racks at the specified
points.
•Before disconnecting connectors of sensors or
units, be sure to disconnect the ground cable from
battery.
(1) Front catalytic converter upper
cover (RH)
(11) Front catalytic converter lower
cover (LH)
(23) Rear exhaust pipe
(24) Cushion rubber
(2) Front catalytic converter lower
cover (RH)
(12) Front exhaust pipe (LH) (25) Self-locking nut
(13) Front catalytic converter (LH) (26) Gasket
(3) Gasket (14) Front oxygen (A/F) sensor (LH)
(4) Front exhaust pipe (RH) (15) Rear oxygen sensor (LH)Tightening torque: N·m (kgf-m, ft-lb)
(5) Front catalytic converter (RH) (16) Muffler (RH)T1: 13 (1.3, 9.4)
(6) Front oxygen (A/F) sensor (RH) (17) Muffler (LH)T2: 18 (1.8, 13.0)
(7) Rear oxygen sensor (RH) (18) Rear catalytic converterT3: 21 (2.1, 15.2)
(8) Gasket (19) BracketT4: 30 (3.1, 22.4)
(9) Gasket (20) GasketT5: 35 (3.6, 26.0)
(10) Front catalytic converter upper
cover (LH)
(21) SpringT6: 48 (4.9, 35.4)
(22) Chamber

EX(H6DO)-4
Front Exhaust Pipe
EXHAUST
2. Front Exhaust Pipe
A: REMOVAL
1) Disconnect the ground cable from battery.
2) Lift-up the vehicle.
3) Remove the under cover.
4) Remove the front oxygen (A/F) sensor connec-
tor (A) and rear oxygen sensor connector (B).
5) Separate the front exhaust pipe from rear ex-
haust pipe.
CAUTION:
Be careful, exhaust pipe is hot.
6) Remove the nuts which hold front exhaust pipe
onto cylinder heads.
CAUTION:
Be careful not to pull down the front exhaust
pipe assembly.
7) Remove the bolts which hold front exhaust pipe
assembly to hanger bracket.
8) Remove the front exhaust pipe assembly from
vehicle.
CAUTION:
•Be careful not to let the front exhaust pipe as-
sembly fall off when removing, since it is very
heavy.
•After removing the front exhaust pipe assem-
bly, do not apply excessive pulling force on the
rear exhaust pipe.
9) Separate the front exhaust pipe (RH) from front
exhaust pipe assembly.
10) Remove the front oxygen (A/F) sensor and rear
oxygen sensor.
EX-02014
(A)
(B)
EX-02015
EX-02016
EX-00061
EX-02017