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 front oxygen sensor.
4.Check front oxygen sensor.
CAUTION:
After repair or replacement of faulty parts, conduct
CLEAR MEMORY and INSPECTION MODES. [T3D0] and [T3E0].>
WIRING DIAGRAM:

LHD model
OBD0201



181
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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.
OBD0215
5) Read data on Subaru Select Monitor or OBD-II general
scan tool.

Subaru Select Monitor
Designate mode using function key.
Function mode: F29

F29: Front oxygen sensor heater current is indicated.
: Is the reading of F29 0.2 A, or more?
: Go to step 2.
: Repair connector.
NOTE:
In this case, poor contact in front oxygen sensor connec-
tor 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.
OBD0216A
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. 44—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.
183
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11. Diagnostics Chart with Trouble Code

OBD0216A
3) Disconnect connector from front oxygen sensor.
4) Measure voltage between ECM and body.
: Connector & terminal
(B84) No. 44—Body/1.0 V, or less
: Replace ECM.
: Repair short circuit of harness between ECM and
front oxygen sensor connector. After repair short
circuit of harness, replace ECM.
OBD0667A
3CHECK POWER SUPPLY TO FRONT OXYGEN
SENSOR.
1) Turn ignition switch to OFF.
2) Disconnect connector from front oxygen sensor.
3) Turn ignition switch to ON.
4) Measure voltage between front oxygen sensor connec-
tor and body.
: Connector & terminal
(B18) 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 front oxygen sen-
sor.
OBD0706
4
CHECK FRONT OXYGEN SENSOR.
1) Turn ignition switch to OFF.
2) Measure resistance between front 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 the front oxygen sen-
sor connector and the ECM connector

2Poor contact in front oxygen sensor connector

3Poor contact in ECM connector
: Replace front oxygen sensor.
184
2-7ON-BOARD DIAGNOSTICS II SYSTEM
11. Diagnostics Chart with Trouble Code

OBD0220
M: DTC P0136
—REAR OXYGEN SENSOR CIRCUIT
MALFUNCTION (RO2
—V)—
DESCRIPTION:

In order to monitor purifying efficiency of the catalyzer,
the rear oxygen sensor sends a signal to the ECM.

Refer to“J: DTC P0130—FRONT OXYGEN SENSOR
CIRCUIT MALFUNCTION—[T11J0]”.
DTC DETECTING CONDITION:

Two consecutive trips with fault
185
2-7ON-BOARD DIAGNOSTICS II SYSTEM
11. Diagnostics Chart with Trouble Code

1.Check DTC P0130 on display.
No
Ye s
2.Check failure cause of P0130.
3.Check rear oxygen sensor data.

4.Check harness.
5.Check exhaust system.
CAUTION:
After repair or replacement of faulty parts, conduct
CLEAR MEMORY and INSPECTION MODES. [T3D0] and [T3E0].>
WIRING DIAGRAM:

LHD model
OBD0221


186
2-7ON-BOARD DIAGNOSTICS II SYSTEM
11. Diagnostics Chart with Trouble Code

1
CHECK DTC P0130 ON DISPLAY.
: Check that Subaru Select Monitor or the
OBD-II general scan tool shows P0130.
: Go to step 2.
: Go to step 3.
2
CHECK FAILURE CAUSE OF P0130.
Perform the step 1 of DTC P0130.
: Is the failure cause of P0130 in the fuel sys-
tem?
: Check fuel system. In this case, inspection of
P0136 is not necessary.
: Go to step 3.
OBD0145A
3
CHECK REAR OXYGEN SENSOR DATA.
1) Turn ignition switch to OFF.
2) Connect Subaru Select Monitor or OBD-II general scan
tool to data link connector.
3) Start the engine, and turn Subaru Select Monitor or
OBD-II general scan tool switch to ON.
4) Warm-up the engine until engine coolant temperature is
above 70°C (160°F), and keep the engine speed at 2,000
rpm to 3,000 rpm for two minutes.
OBD0225
5) Read data on Subaru Select Monitor or OBD-II general
scan tool.

Subaru Select Monitor
Designate mode using function key.
Function mode: F16

F16: Rear oxygen sensor output signal is indicated.
: Is the indicated data fluctuate?
: Go to step 5.
: Go to next.
: Is the indicated data fixed at 0.3±0.1 V?
: Go to step 4.
: Replace rear oxygen sensor.

OBD-II general scan tool
For detailed operation procedures, refer to the OBD-II Gen-
eral Scan Tool Instruction Manual.
188
2-7ON-BOARD DIAGNOSTICS II SYSTEM
11. Diagnostics Chart with Trouble Code

4
CHECK HARNESS.
1) Turn ignition switch to OFF.
2) Disconnect connector from rear oxygen sensor.
3) Turn ignition switch to ON.
OBD0707A
4) Measure voltage between rear oxygen sensor harness
connector and body.
: Connector & terminal
(T6) No. 4—Body/0.2 V, or more
: Repair harness and connector.
NOTE:
In this case, the following are the possible causes.

1Open circuit of harness between rear oxygen sensor
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.
5
CHECK EXHAUST SYSTEM.
: Check the following items.

Looseness of installation portions

Damage (crack, hole etc.) of parts

Looseness and opening of parts between
front oxygen sensor and rear oxygen sen-
sor.
: Repair or replace faulty parts.
: Replace rear oxygen sensor.
189
2-7ON-BOARD DIAGNOSTICS II SYSTEM
11. Diagnostics Chart with Trouble Code

OBD0229
N: DTC P0139
—REAR OXYGEN SENSOR CIRCUIT SLOW
RESPONSE (RO2
—R)—
DESCRIPTION:
Refer to“M: DTC P0136—REAR OXYGEN SENSOR
CIRCUIT MALFUNCTION—[T11M0]”.
DTC DETECTING CONDITION:

Two consecutive trips with fault
190
2-7ON-BOARD DIAGNOSTICS II SYSTEM
11. Diagnostics Chart with Trouble Code

1.Check DTC P0136 on display.
No
Ye s

Inspect DTC P0136 using“11. Diagnostics Chart
with Trouble Code [T1100]”.

In this case, it is unnecessary to inspect DTC
P0139.
2.Replace 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

191
2-7ON-BOARD DIAGNOSTICS II SYSTEM
11. Diagnostics Chart with Trouble Code

OBD0232
O: DTC P0141
—REAR OXYGEN SENSOR HEATER
CIRCUIT MALFUNCTION (RO2H)—
DESCRIPTION:
Refer to“M: DTC P0136—REAR OXYGEN SENSOR
CIRCUIT MALFUNCTION—[T11M0]”.
DTC DETECTING CONDITION:

Two consecutive trips with fault
193
2-7ON-BOARD DIAGNOSTICS II SYSTEM
11. Diagnostics Chart with Trouble Code