SUBARU LEGACY 1995 Service Repair Manual

4
CHECK VACUUM HOSE.
: Check for disconnection, holes, or clogging
of the vacuum hoses.
NOTE:
Check the hoses;

From pressure sources switching solenoid valve to
intake manifold.

From pressure sensor to pressure sources switching
solenoid valve.
: Repair hoses.
: Go to step 5.
5CHECK PRESSURE SOURCES OF SWITCH-
ING SOLENOID VALVE.
1) Turn ignition switch to OFF.
2) Connect test mode connector.
3) Turn ignition switch to ON.
: Is operation sound of the pressure sources
solenoid valve heard? (ON↔OFF each 1.5
sec.)
: Replace pressure sensor.
: Replace pressure sources switching solenoid
valve.
155
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11. Diagnostics Chart with Trouble Code

OBD0172
F: DTC P0115
—ENGINE COOLANT TEMPERATURE
SENSOR CIRCUIT MALFUNCTION (TW)—
OBD0173A
DESCRIPTION:
The engine coolant temperature sensor is located on the
engine coolant pipe which is made of aluminum alloy. Its
thermistor changes resistance with respect to temperature.
A engine coolant temperature signal converted into resis-
tance is transmitted to the ECM to control the amount of
fuel injection, ignition timing, purge control solenoid valve,
etc.
DTC DETECTING CONDITION:

Immediately at fault recognition
TROUBLE SYMPTOM:

Hard to start

Erroneous idling

Poor driving performance
156
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11. Diagnostics Chart with Trouble Code

1.Connect Subaru Select Monitor or the OBD-II
general scan tool, and read data.

2.Check harness.
3.Check harness.
CAUTION:
After repair or replacement of faulty parts, conduct
CLEAR MEMORY and INSPECTION MODES. <Ref. to
[T3D0] and [T3E0].>
WIRING DIAGRAM:
OBD0174

157
2-7ON-BOARD DIAGNOSTICS II SYSTEM
11. Diagnostics Chart with Trouble Code

OBD0145A
1CONNECT SUBARU SELECT MONITOR OR
THE OBD-II GENERAL SCAN TOOL, AND
READ DATA.
1) Turn ignition switch to OFF.
2) Connect Subaru Select Monitor or the OBD-II general
scan tool to data link connector.
3) Turn ignition switch to ON and Subaru Select Monitor or
OBD-II general scan tool switch to ON.
4) Start engine.
OBD0176
OBD0177
5) Read data on Subaru Select Monitor or OBD-II general
scan tool.

Subaru Select Monitor
Designate mode using function key.
Function mode: F05 or F06

F05: Water temperature is indicated in“°F”.

F06: Water temperature is indicated in“°C”.
:
Is the value greater than 300°F with func-
tion mode F05?

Is the value greater than 150°C with func-
tion mode F06?
: Go to step 2.
: Go to next.
:
Is the value less than 40°F with function
mode F05?

Is the value less than 40°C with function
mode F06?
: Go to step 3.
: Repair poor contact in connectors or harness.

Engine coolant temperature sensor connector

ECM connector

Coupling connector (B21)

OBD-II general scan tool
For detailed operation procedures, refer to the OBD-II Gen-
eral Scan Tool Instruction Manual.
OBD0618A
2
CHECK HARNESS.
1) Turn ignition switch to OFF.
2) Remove idle air control solenoid valve by-pass air hose.
3) Disconnect connector from engine coolant temperature
sensor.
158
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11. Diagnostics Chart with Trouble Code

OBD0145A
4) Connect Subaru Select Monitor or the OBD-II general
scan tool to data link connector.
OBD0176
OBD0177
5) Turn ignition switch and Subaru Select Monitor or
OBD-II general scan tool switch to ON.
6) Read data on Subaru Select Monitor or the OBD-II gen-
eral scan tool.

Subaru Select Monitor
Designate mode using function key.
Function mode: F05 or F06

F05: Water temperature is indicated in“°F”.

F06: Water temperature is indicated in“°C”.
:
Is the value less than40°F with function
mode F05?

Is the value less than40°C with function
mode F06?
: Replace engine coolant temperature sensor.
: Repair short circuit of harness between engine
coolant temperature sensor connector and ECM
connector.

OBD-II general scan tool
For detailed operation procedures, refer to the OBD-II Gen-
eral Scan Tool Instruction Manual.
159
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11. Diagnostics Chart with Trouble Code

OBD0618A
3
CHECK HARNESS.
1) Turn ignition switch to OFF.
2) Remove idle air control solenoid valve by-pass air hose.
3) Disconnect connector from engine coolant temperature
sensor.
4) Turn ignition switch to ON.
OBD0696A
5) Measure voltage between engine coolant temperature
sensor and body.
: Connector & terminal
(E8) No. 1—Body/4 V, or more
: Repair open circuit of harness or poor contact in
ECM and engine coolant temperature sensor con-
nector.
: Go to the next step.
6) Turn ignition switch to OFF.
OBD0697A
7) Measure resistance of harness between engine coolant
temperature sensor connector and body.
: Connector & terminal
(E8) No. 2—Body/10Ω, or less
: Repair open circuit of harness or poor contact in
ECM and engine coolant temperature sensor con-
nector.
: Replace engine coolant temperature sensor.
160
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11. Diagnostics Chart with Trouble Code

OBD0181
G: DTC P0120
—THROTTLE POSITION SENSOR CIRCUIT
MALFUNCTION (THV)—
OBD0182A
DESCRIPTION:

A throttle position sensor is provided with a potentiom-
eter which is interlocked with the throttle valve shaft.

This throttle position sensor sends the ECM a potenti-
ometer output signal corresponding to the opening of the
throttle valve. When the level of this signal exceeds a pre-
determined value, the ECM interprets it as complete clo-
sure of the throttle valve and makes a control most suitable
for the engine operation with the throttle valve fully closed.
For correcting error of this signal, the ECM is provided with
a learning function.

Thus, the ECM precisely controls the air-fuel ratio dur-
ing acceleration and deceleration as well as engine idling.
DTC DETECTING CONDITION:

Immediately at fault recognition
TROUBLE SYMPTOM:

Erroneous idling

Engine stalls.

Poor driving performance
161
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11. Diagnostics Chart with Trouble Code

1.Connect Subaru Select Monitor or OBD-II
general scan tool and read data.

2.Check input signal for ECM. (Using voltage
meter and Subaru select monitor.)
3.Check harness connector between ECM and
throttle position sensor.
4.Check harness connector between throttle
position sensor and body.
CAUTION:
After repair or replacement of faulty parts, conduct
CLEAR MEMORY and INSPECTION MODES. <Ref. to
[T3D0] and [T3E0].>
WIRING DIAGRAM:
OBD0183


162
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11. Diagnostics Chart with Trouble Code

OBD0145A
1CONNECT SUBARU SELECT MONITOR OR
THE OBD-II GENERAL SCAN TOOL, AND
READ DATA.
1) Turn ignition switch to OFF.
2) Connect Subaru Select Monitor or the OBD-II general
scan tool to data link connector.
3) Turn ignition switch to ON and Subaru Select Monitor or
OBD-II general scan tool switch to ON.
4) Start engine.
OBD0185
5) Read data on Subaru Select Monitor or OBD-II general
scan tool.

Subaru Select Monitor
Designate mode using function key.
Function mode: F10

F10: Throttle position sensor output signal is indicated.
: Is the voltage less than 0.1 V?
: Go to step 2.
: Go to next.
: Is the voltage more than 4.9 V?
: Go to step 4.
: Even if MIL lights up, the circuit has returned to a
normal condition at this time. A temporary poor
contact of the connector may be the cause. Check
and repair the following connectors.

Throttle position sensor connector.

ECM connector

Coupling connector (B21)

OBD-II general scan tool
For detailed operation procedures, refer to the OBD-II Gen-
eral Scan Tool Instruction Manual.
163
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11. Diagnostics Chart with Trouble Code

OBD0698A
2CHECK INPUT SIGNAL FOR ECM. (USING
VOLTAGE METER AND SUBARU SELECT
MONITOR.)
1) Measure voltage between ECM and body while throttle
valve is fully closed.
: Connector & terminal
(B84) No. 22—Body/4.5 V, or more
: Go to next step.
: Go to next.
: Is the voltage more than 4.5 V while shaking
harness and connector of ECM?
: Repair poor contact in ECM connector.
: Replace ECM.
OBD0699A
2) Measure signal voltage between ECM and body.
: Connector & terminal
(B84) No. 24—Body/0.1 V, or less
: Go to next.
: Go to step 3.
: Is the voltage more than 0.1 V while shaking
harness and connector of ECM and monitor-
ing the value with Subaru select monitor?
: Repair poor contact in ECM connector.
: Go to step 3.
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11. Diagnostics Chart with Trouble Code