Subaru Legacy III (2000-2003 year). Manual - part 330

EN(H6DO)-122

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

Step

Value

Yes

No

1

CHECK OUTPUT SIGNAL FROM ECM.
1) Turn ignition switch to ON.
2) Measure voltage between ECM connector 

and chassis ground.

Connector & terminal

(B137) No. 6 (+) — Chassis ground (

−−−−

):

Does the measured value exceed the spec-
ified value?

8 V

Go to step 3.

Go to step 2.

2

CHECK OUTPUT SIGNAL FROM ECM.
Measure voltage between ECM connector and 
chassis ground.

Connector & terminal

(B137) No. 7 (+) — Chassis ground (

−−−−

):

Does the measured value exceed the specified 
value?

8 V

Go to step 3.

Go to step 4.

3

CHECK FRONT OXYGEN (A/F) SENSOR 
HEATER CURRENT.
1) Turn ignition switch to OFF.
2) Repair battery short circuit in harness 

between ECM and front oxygen (A/F) sen-
sor connector.

3) Turn ignition switch to ON.
4) Read data of front oxygen (A/F) sensor 

heater current using Subaru Select Monitor 
or the 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 procedure, refer to the 
OBD-II General Scan Tool Instruction Manual.

2.3 A

Replace ECM. 
<Ref. to 
FU(H6DO)-46, 
Engine Control 
Module.>

END

4

CHECK OUTPUT SIGNAL FROM ECM.
Measure voltage between ECM connector and 
chassis ground.

Connector & terminal

(B137) No. 6 (+) — Chassis ground (

−−−−

):

Does the voltage change more than the speci-
fied value shaking harness and connector of 
ECM while monitoring the value with voltage 
meter?

8 V

Repair battery 
short circuit in har-
ness between 
ECM and front 
oxygen (A/F) sen-
sor connector.

Go to step 5.

5

CHECK OUTPUT SIGNAL FROM ECM.
Measure voltage between ECM connector and 
chassis ground.

Connector & terminal

(B137) No. 7 (+) — Chassis ground (

−−−−

):

Does the voltage change more than the speci-
fied value by shaking harness and connector 
of ECM while monitoring the value with voltage 
meter?

8 V

Repair battery 
short circuit in har-
ness between 
ECM and front 
oxygen (A/F) sen-
sor connector.

END

EN(H6DO)-123

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

MEMO:

EN(H6DO)-124

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

I:

DTC P0068 — MANIFOLD ABSOLUTE PRESSURE/BAROMETRIC PRES-
SURE CIRCUIT RANGE/PERFORMANCE —

• DTC DETECTING CONDITION:

• Two consecutive driving cycles with fault

• TROUBLE SYMPTOM

• Erroneous idling

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.>.

• WIRING DIAGRAM:

EN-00811

9

19

8

5

8

B135

B20

E1

16

13

14

B83

E21

1 2 3

B83

B20

B135

ECM

3

2

1

E21

INTAKE MANIFOLD
PRESSURE SENSOR

THROTTLE BODY

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

1 2 3 4
5 6 7 8
9 10 11 12

13 14 15 16

1 2 3 4

5 6 7 8 9 10

11 12

19 20

13 14 15 16 17 18

EN(H6DO)-125

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

Step

Value

Yes

No

1

CHECK IDLE SWITCH SIGNAL.
1) Turn ignition switch to ON.
2) Operate the LED operation mode for 

engine using Subaru Select Monitor.
Does the LED of {Idle Switch Signal} come 
on?

NOTE:

• Subaru Select Monitor
For detailed operation procedure, refer to the 
“LED OPERATION MODE FOR ENGINE”. 
<Ref. to EN(H6DO)-34, Subaru Select Moni-
tor.>

LED comes on.

Go to step 2.

Check throttle 
position sensor cir-
cuit. <Ref. to 
EN(H6DO)-148, 
DTC P0121 — 
THROTTLE/
PEDAL POSI-
TION SENSOR/
SWITCH “A” CIR-
CUIT RANGE/
PERFORMANCE 
—, Diagnostic Pro-
cedure with Diag-
nostic Trouble 
Code (DTC).>

NOTE:
In this case, it is
not necessary to
inspect DTC
P0106.

2

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).>

NOTE:
In this case, it is
not necessary to
inspect DTC
P0106.

Go to step 3.

3

CHECK CONDITION OF INTAKE MANIFOLD 
PRESSURE SENSOR.
Is the intake manifold pressure sensor installa-
tion bolt tightened securely?

Tightened securely.

Go to step 4.

Tighten intake 
manifold pressure 
sensor installation 
bolt securely.

4

CHECK CONDITION OF THROTTLE BODY.
Is the throttle body installation bolt tightened 
securely?

Tightened securely.

Go to step 5.

Tighten throttle 
body installation 
bolt securely.

5

CHECK CONDITION OF EGR VALVE.
Is there any foreign object caught between 
EGR solenoid valve and intake manifold?

There is a foreign object.

Completely 
remove foreign 
object, and install 
EGR solenoid 
valve securely to 
the intake mani-
fold.

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