1996 SUBARU LEGACY Chassis

B2M0541A
10G2CHECK INPUT SIGNAL FOR ECM.
(USING VOLTAGE METER AND SUBARU
SELECT MONITOR.)
1) Measure voltage between ECM connector and chassis
ground while throttle valve is fully closed.
: Connector & terminal
(B84) No. 21 (+)—Chassis ground ():
Is the voltage more than 4.5 V?
: Go to next step 2).
: Go to next.
: Does the voltage change more than 4.5 V by
shaking harness and connector of ECM
while monitoring the value with voltage
meter?
: Repair poor contact in ECM connector.
: Replace ECM.
B2M0542A
2) Measure voltage between ECM connector and chassis
ground.
: Connector & terminal
(B84) No. 6 (+)—Chassis ground ():
Is the voltage less than 0.1 V?
: Go to step10G3.
: Go to next.
B2M0482
: Does the voltage change more than 0.1 V by
shaking harness and connector of ECM
while monitoring the value with Subaru
select monitor?
: Repair poor contact in ECM connector.
: Go to step10G3.
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2-7ON-BOARD DIAGNOSTICS II SYSTEM
10. Diagnostics Chart with Trouble Code

10L1
CHECK DTC P0141 ON DISPLAY.
: Does the Subaru select monitor or OBD-II
general scan tool indicate DTC P0135 and
P0141 at the same time?
: Go to next step 1).
: Go to step10L2.
B2M0547A
1) Turn ignition switch to OFF.
2) Disconnect connector from ECM.
3) Measure resistance of harness between ECM connec-
tor and chassis ground.
: Connector & terminal
(B84) No. 42—Chassis ground:
Is the resistance less than 5Ω?
: Repair poor contact in ECM connector.
: Repair harness and connector.
NOTE:
In this case, repair the following:

Open circuit in harness between ECM and coupling con-
nector (B22)

Open circuit in harness between coupling connector
(B22) and engine grounding terminal

Poor contact in front oxygen sensor connector

Poor contact in coupling connector (B22)
169
2-7ON-BOARD DIAGNOSTICS II SYSTEM
10. Diagnostics Chart with Trouble Code

OBD0145A
10L2CONNECT 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.
B2M0497
5) Read data on Subaru Select Monitor or OBD-II general
scan tool.

Subaru Select Monitor
Designate mode using function key.
Function mode: F32

F32: Front oxygen sensor heater current is indicated.
: Is the value more than 0.2 A in function
mode F32?
: Repair connector.
NOTE:
In this case, repair the following:

Poor contact in front oxygen sensor connector

Poor contact in ECM connector
: Go to step10L3.

OBD-II scan tool
For detailed operation procedures, refer to the OBD-II Gen-
eral Scan Tool Instruction Manual.
B2M0548A
10L3CHECK OUTPUT SIGNAL FROM ECM.
(USING VOLTAGE METER.)
1) Start and idle the engine.
2) Measure voltage between ECM connector and chassis
ground.
: Connector & terminal
(B84) No. 38 (+)—Chassis ground ():
Is the voltage less than 1.0 V?
: Go to step10L4.
: Go to next.
: Does the voltage change less than 1.0 V by
shaking harness and connector of ECM
while monitoring the value with voltage
meter?
: Repair poor contact in ECM connector.
: Go to next step 3).
170
2-7ON-BOARD DIAGNOSTICS II SYSTEM
10. Diagnostics Chart with Trouble Code

B2M0548A
3) Disconnect connector from front oxygen sensor.
4) Measure voltage between ECM connector and chassis
ground.
: Connector & terminal
(B84) No. 38 (+)—Chassis ground ():
Is the voltage less than 1.0 V?
: Replace ECM.
: Repair short circuit in harness between ECM and
front oxygen sensor connector. After repair short
circuit of harness, replace ECM.
B2M0549A
10L4CHECK 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 engine ground.
: Connector & terminal
(B18) No. 2 (+)—Engine ground ():
Is the voltage more than 10 V?
: Go to step10L5.
: Repair power supply line.
NOTE:
In this case, repair the following:

Open circuit in harness between main relay and front
oxygen sensor connector

Poor contact in front oxygen sensor connector

Poor contact in main relay connector
B2M0768
10L5
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:
Is the resistance less than 30Ω?
: Repair harness and connector.
NOTE:
In this case, repair the following:

Open circuit in harness between front oxygen sensor
and ECM connector

Poor contact in front oxygen sensor connector

Poor contact in ECM connector
: Replace front oxygen sensor.
171
2-7ON-BOARD DIAGNOSTICS II SYSTEM
10. Diagnostics Chart with Trouble Code

B2M0488
: Is the value fixed between 0.2 and 0.4 V in
function mode F13?
: Go to step10M4.
: Replace rear oxygen sensor.

OBD-II general scan tool
For detailed operation procedures, refer to the OBD-II Gen-
eral Scan Tool Instruction Manual.
OBD0707C
10M4CHECK HARNESS BETWEEN REAR
OXYGEN SENSOR AND ECM CONNEC-
TOR.
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 harness
connector and engine ground or chassis ground.
: Connector & terminal

2200 cc California model
(B19) No. 4 (+)—Engine ground ():

Except 2200 cc California model
(T6) No. 4 (+)—Chassis ground ():
Is the voltage more than 0.2 V?
: Replace rear oxygen sensor.
: Repair harness and connector.
NOTE:
In this case, repair the following:

Open circuit in harness between rear oxygen sensor and
ECM connector

Poor contact in rear oxygen sensor connector

Poor contact in ECM connector

Poor contact in rear oxygen sensor connecting harness
connector (Except 2200 cc California model)
10M5
CHECK EXHAUST SYSTEM.
: Is there a fault in exhaust system?
NOTE:
Check the following items.

Loose installation of portions

Damage (crack, hole etc.) of parts

Looseness and ill fitting of parts between front oxygen
sensor and rear oxygen sensor
: Repair or replace faulty parts.
: Replace rear oxygen sensor.
176
2-7ON-BOARD DIAGNOSTICS II SYSTEM
10. Diagnostics Chart with Trouble Code

B2M0553A
1) Turn ignition switch to OFF.
2) Disconnect connector from ECM.
3) Measure resistance of harness between ECM connec-
tor and chassis ground.
: Connector & terminal
(B84) No. 42—Chassis ground:
Is the resistance less than 5Ω?
: Repair poor contact in ECM connector.
: Repair harness and connector.
NOTE:
In this case, repair the following:

Open circuit in harness between ECM and coupling con-
nector (B22)

Open circuit in harness between coupling connector
(B22) and engine grounding terminal

Poor contact in rear oxygen sensor connector

Poor contact in rear oxygen sensor connecting harness
connector (B19)

Poor contact in coupling connector (B22)
OBD0145A
10O2CONNECT 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.
B2M0498
5) Read data on Subaru Select Monitor or OBD-II general
scan tool.

Subaru Select Monitor
Designate mode using function key.
Function mode: F33

F33: Rear oxygen sensor heater current is indicated.
: Is the value more than 0.2 A in function
mode F33?
: Repair connector.
NOTE:
In this case, repair the following:

Poor contact in rear oxygen sensor connector

Poor contact in rear oxygen sensor connecting harness
connector

Poor contact in ECM connector
: Go to step10O3.

OBD-II scan tool
For detailed operation procedures, refer to the OBD-II Gen-
eral Scan Tool Instruction Manual.
182
2-7ON-BOARD DIAGNOSTICS II SYSTEM
10. Diagnostics Chart with Trouble Code

B2M0554A
10O3CHECK OUTPUT SIGNAL FROM ECM.
(USING VOLTAGE METER.)
1) Start and idle the engine.
2) Measure voltage between ECM connector and chassis
ground.
: Connector & terminal
(B84) No. 37 (+)—Chassis ground ():
Is the voltage less than 1.0 V?
: Go to step10O4.
: Go to next.
: Does the voltage change less than 1.0 V by
shaking harness and connector of ECM
while monitoring the value with voltage
meter?
: Repair poor contact in ECM connector.
: Go to next step 3).
B2M0554A
3) Disconnect connector from rear oxygen sensor.
4) Measure voltage between ECM connector and chassis
ground.
: Connector & terminal
(B84) No. 37 (+)—Chassis ground ():
Is the voltage less than 1.0 V?
: Replace ECM.
: Repair short circuit in harness between ECM and
rear oxygen sensor connector. After repair short
circuit in harness, replace ECM.
183
2-7ON-BOARD DIAGNOSTICS II SYSTEM
10. Diagnostics Chart with Trouble Code

OBD0710C
10O4CHECK POWER SUPPLY TO REAR OXY-
GEN 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 engine ground or chassis ground.
: Connector & terminal

2200 cc California model
(B19) No. 2 (+)—Engine ground ():

Except 2200 cc California model
(T6) No. 2 (+)—Chassis ground ():
Is the voltage more than 10 V?
: Go to step10O5.
: Repair power supply line.
NOTE:
In this case, repair the following:

Open circuit in harness between main relay and rear
oxygen sensor connector

Poor contact in rear oxygen sensor connector

Poor contact in rear oxygen sensor connecting harness
connector (Except 2200 cc California model)
OBD0706
10O5
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:
Is the resistance less than 30Ω?
: Repair harness and connector.
NOTE:
In this case, repair the following:

Open circuit in harness between rear oxygen sensor and
ECM connector

Poor contact in rear oxygen sensor connector

Poor contact in ECM connector

Poor contact in rear oxygen sensor connecting harness
connector
: Replace rear oxygen sensor.
184
2-7ON-BOARD DIAGNOSTICS II SYSTEM
10. Diagnostics Chart with Trouble Code