sensor SUBARU LEGACY 1995 Service Repair Manual

1.Connect Subaru Select Monitor or the OBD-II
general scan tool, and read data.
2.Check output signal from ECM. (Using voltage
meter.)
3.Check power supply to rear oxygen sensor.
4.Check rear oxygen sensor.
CAUTION:
After repair or replacement of faulty parts, conduct
CLEAR MEMORY and INSPECTION MODES. [T3D0] and [T3E0].>
WIRING DIAGRAM:

LHD model
OBD0221



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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.
OBD0708
5) Read data on Subaru Select Monitor or OBD-II general
scan tool.

Subaru Select Monitor
Designate mode using function key.
Function mode: F30

F30: Rear oxygen sensor heater current is indicated.
: Is the reading of F30 0.2 A, or more?
: Go to step 2.
: Repair connector.
NOTE:
In this case, poor contact of rear oxygen sensor connector
and ECM connector can be the possible cause.

OBD-II scan tool
For detailed operation procedures, refer to the OBD-II Gen-
eral Scan Tool Instruction Manual.
OBD0709A
2CHECK OUTPUT SIGNAL FROM ECM. (USING
VOLTAGE METER.)
1) Start and idle the engine.
2) Measure voltage between ECM and body.
: Connector & terminal
(B84) No. 43—Body/1.0 V, or less
: Go to step 3.
: Go to next.
: Is the voltage less than 1.0 V while shaking
harness and connector of ECM?
: Repair poor contact in ECM connector.
: Go to next step.
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11. Diagnostics Chart with Trouble Code

OBD0709A
3) Disconnect connector from rear oxygen sensor.
4) Measure voltage between ECM and body.
: Connector & terminal
(B84) No. 43—Body/1.0 V, or less
: Replace ECM.
: Repair short circuit of harness between ECM and
rear oxygen sensor connector. After repair short
circuit of harness, replace ECM.
OBD0710A
3CHECK POWER SUPPLY TO REAR OXYGEN
SENSOR.
1) Turn ignition switch to OFF.
2) Disconnect connector from rear oxygen sensor.
3) Turn ignition switch to ON.
4) Measure voltage between rear oxygen sensor connec-
tor and body.
: Connector & terminal
(T6) No. 2—Body/10 V, or more
: Go to step 4.
: Repair power supply line.
NOTE:
In this case, repair poor contact in connector or open cir-
cuit of harness between main relay and rear oxygen sen-
sor.
OBD0706
4
CHECK REAR OXYGEN SENSOR.
1) Turn ignition switch to OFF.
2) Measure resistance between rear oxygen sensor con-
nector terminals.
: Terminals
No. 1—No. 2/30Ω, or less
: Repair harness and connector.
NOTE:
In this case, repair the following.

1Open circuit of harness between rear oxygen sensor
connector and ECM connector

2Poor contact in rear oxygen sensor connector

3Poor contact in ECM connector

4Poor contact in rear oxygen sensor connecting harness
connector
: Replace rear oxygen sensor.
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11. Diagnostics Chart with Trouble Code

OBD0240
P: DTC P0170
—FUEL TRIM MALFUNCTION (FUEL)—
DTC DETECTING CONDITION:

Two consecutive trips with fault
TROUBLE SYMPTOM:

Erroneous idling

Engine stalls.

Poor driving performance
1.Check exhaust system.
2.Check air intake system.
3.Check fuel pressure.
4.Check engine coolant temperature sensor.

5.Check mass air flow sensor.
CAUTION:
After repair or replacement of faulty parts, conduct
CLEAR MEMORY and INSPECTION MODE. [T3D0] and [T3E0].>




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11. Diagnostics Chart with Trouble Code

4CHECK ENGINE COOLANT TEMPERATURE
SENSOR.
< REF. TO“F: DTC P0115 [T11F0].”>
1) Turn ignition switch to OFF.
OBD0145A
2) Connect the Subaru Select Monitor or the OBD-II gen-
eral scan tool to data link connector.
3) Start the engine and warm-up completely.
OBD0176
OBD0177
4) 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 temperature indicated on Subaru Select
Monitor (F05) greater than 140°F?
Is temperature indicated on Subaru Select
Monitor (F06) greater than 60°C?
: Go to step 5.
: Replace engine coolant temperature sensor.

OBD-II general scan tool
For detailed operation procedures, refer to the OBD-II Gen-
eral Scan Tool Instruction Manual.
201
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11. Diagnostics Chart with Trouble Code

OBD0145A
5
CHECK MASS AIR FLOW SENSOR.
1) Turn ignition switch to OFF.
2) Connect the Subaru Select Monitor or the OBD-II gen-
eral scan tool to data link connector.
3) Start the engine and warm-up engine until coolant tem-
perature is greater than 60°C (140°F).
OBD0616
4) Read data on Subaru Select Monitor or OBD-II general
scan tool.

Subaru Select Monitor
Designate mode using function key.
Function mode: F47

F47: Mass air flow is shown on display.
: Is the voltage within the specifications
shown in the following table?
Engine speed Specified value
Idling 1.9—3.6 (g/sec)
2,500 rpm 7.0—14.8 (g/sec)
: Replace mass air flow sensor.
: Contact with SOA service.
Note: Inspection by DTM is required.
Probable cause: Deterioration of plural parts

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

OBD0283
Y: DTC P0325
—KNOCK SENSOR CIRCUIT MALFUNCTION
(KNOCK)—
OBD0284A
DESCRIPTION:
The knock sensor senses engine knocks and send a volt-
age signal to the ECM depending on the degree of the
knock.
This signal information is used for spark timing learning
control to provide optimal spark timing.
The knock sensor is bolted to the cylinder block at #4 pis-
ton. It senses knocks which can occur in any cylinder. Its
components are a weight, which moves up and down when
it senses vibrations, a piezo element, which produces a
voltage, and a resistor, which senses a broken circuit (all
these are molded into a single unit). When the sensor
senses engine knocks, knocking vibration is conveyed to
the weight. The up or down movement of the weight is
applied to the piezo element as a pressure difference. The
knock sensor will then produce a voltage signal in relation
to the degree of the knock.
DTC DETECTING CONDITION:

Immediately at fault recognition
TROUBLE SYMPTOM:

Poor driving performance

Knocking occurs.
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11. Diagnostics Chart with Trouble Code

1.Check harness.


2.Check knock sensor.
3.Check knock sensor.
4.Check input signal for ECM.
CAUTION:
After repair or replacement of faulty parts, conduct
CLEAR MEMORY and INSPECTION MODES.

WIRING DIAGRAM:
OBD0285

218
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11. Diagnostics Chart with Trouble Code

OBD0716A
1
CHECK HARNESS.
1) Turn ignition switch to OFF.
2) Disconnect connector from ECM.
3) Measure resistance between ECM harness connector
and body.
: Connector & terminal
(B84) No. 30—Body/700 kΩ, or more
: Go to step 2.
: Go to next.
OBD0716A
: Connector & terminal
(B84) No. 30—Body/400 kΩ, or less
: Go to step 3.
: Go to step 4.
B2M0244A
2
CHECK KNOCK SENSOR.
1) Disconnect connector from knock sensor.
2) Measure voltage between knock sensor connector and
body.
: Connector & terminal
(E14) No. 1—Body/700 kΩ, or more
: Check and repair the following items.

Open circuit of the harness between knock sen-
sor connector and ECM connector

Poor contact of the knock sensor connector

Poor contact of coupling connector (B21)
: Go to next.
: Check for secure tightening of the knock
sensor installation bolts.
: Tighten knock sensor installation bolts securely.
: Replace knock sensor.
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11. Diagnostics Chart with Trouble Code

OBD0717A
3
CHECK KNOCK SENSOR.
1) Disconnect connector from knock sensor.
2) Measure resistance of harness between knock sensor
connector and body.
: Connector & terminal
(E14) No. 1—Body/400 kΩ, or less
: Replace knock sensor.
: Repair short circuit of harness between knock
sensor connector and ECM connector.
NOTE:
The harness between both connectors is shielded. Repair
short circuit of harness together with shield.
B2M0625A
4
CHECK INPUT SIGNAL FOR ECM.
1) Connect connectors to ECM and knock sensor.
2) Turn ignition switch to ON.
3) Measure voltage between ECM and body.
: Connector & terminal
(B84) No. 30—Body/2 V, or more
: Repair poor contact in ECM connector.
: Even if MIL lights up, the circuit has returned to a
normal condition at this time. (However, the pos-
sibility of poor contact still remains.)
Check and repair the following connectors.

Knock sensor connector

ECM connector

Coupling connector (B21)
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11. Diagnostics Chart with Trouble Code