1997 SUBARU LEGACY check engine

10N1CHECK FOR OTHER CAUSES AFFECT-
ING EXHAUST GAS.
: Is CO % more than 2 % after engine warm-
up?
: Check fuel system.
NOTE:

Check for use of improper fuel.

Check if engine oil or coolant level is extremely low.
: Go to step10N2.
OBD0145A
10N2
CHECK FRONT OXYGEN SENSOR DATA.
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 engine and Turn the Subaru Select Monitor and
the OBD-II general scan tool switch to ON.
4) Warm-up the engine until coolant temperature is above
70°C (160°F) and keep the engine speed at 2,000 rpm to
3,000 rpm for one minute.
B2M0487
5) Read data on Subaru Select Monitor or the OBD-II gen-
eral scan tool.

Subaru Select Monitor
Designate mode using function key.
Function mode: F12

F12: Front oxygen sensor max. and min. output signals
are indicated at the same time.
: Is the difference of voltage less than 0.1 V
between the value of max. output and min.
output with function mode F12?
: Go to step10N3.
: Replace front oxygen sensor.

OBD-II general scan tool
For detailed operation procedures, refer to the OBD-II Gen-
eral Scan Tool Instruction Manual.
173
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10. Diagnostic Chart with Trouble Code for LHD Vehicles

B2M1073A
10N3CHECK HARNESS BETWEEN FRONT
OXYGEN SENSOR AND ECM CONNEC-
TOR.
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 harness
connector and engine ground.
: Connector & terminal
(B18) No. 3 (+)—Engine ground ():
Is the voltage more than 0.2 V?
: Go to next.
: Repair harness and connector.
NOTE:
In this case, repair the following:

Open circuit in harness between ECM and front oxygen
sensor connector

Poor contact in the ECM connector
: Is there poor contact in front oxygen sensor
connector?
: Repair poor contact in front oxygen sensor con-
nector.
: Replace front oxygen sensor.
174
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10. Diagnostic Chart with Trouble Code for LHD Vehicles

10P1
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 step10P2.
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)
OBD0145A
10P2CONNECT 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.
178
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10. Diagnostic Chart with Trouble Code for LHD Vehicles

NOTE:
In this case, repair the following:

Poor contact in front oxygen sensor connector

Poor contact in ECM connector
: Go to step10P3.

OBD-II scan tool
For detailed operation procedures, refer to the OBD-II Gen-
eral Scan Tool Instruction Manual.
B2M0548A
10P3CHECK 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 step10P4.
: 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).
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 battery short circuit in harness between
ECM and front oxygen sensor connector. After
repair, replace ECM.
B2M1075A
10P4CHECK 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?
179
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10. Diagnostic Chart with Trouble Code for LHD Vehicles

10Q1
CHECK DTC P0130 ON DISPLAY.
: Does the Subaru select monitor or OBD-II
general scan tool indicate DTC P0130?
: Go to step10Q2.
: Go to step10Q3.
10Q2
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.
NOTE:
In this case, it is not necessary to inspect DTC P0136.
: Go to step10Q3.
OBD0145A
10Q3
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.
B2M0488
5) Read data on Subaru Select Monitor or OBD-II general
scan tool.

Subaru Select Monitor
Designate mode using function key.
Function mode: F13

F13: Rear oxygen sensor output signal is indicated.
: Does the value fluctuate in function mode
F13?
: Go to step10Q5.
: Go to next.
182
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10. Diagnostic Chart with Trouble Code for LHD Vehicles

B2M0488
: Is the value fixed between 0.2 and 0.4 V in
function mode F13?
: Go to step10Q4.
: 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
10Q4CHECK 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 spec. vehicles
(B19) No. 4 (+)—Engine ground ():

Except 2200 cc California spec. vehicles
(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 spec. vehicles)
10Q5
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.
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10. Diagnostic Chart with Trouble Code for LHD Vehicles

10S1
CHECK DTC P0135 ON DISPLAY.
: Does the Subaru select monitor or OBD-II
general scan tool indicate DTC P0141 and
P0135 at the same time?
: Go to next step 1).
: Go to step10S2.
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
10S2CONNECT 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.
187
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10. Diagnostic Chart with Trouble Code for LHD Vehicles

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 step10S3.

OBD-II scan tool
For detailed operation procedures, refer to the OBD-II Gen-
eral Scan Tool Instruction Manual.
B2M0554A
10S3CHECK 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 step10S4.
: 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 battery short circuit in harness between
ECM and rear oxygen sensor connector. After
repair, replace ECM.
OBD0710C
10S4CHECK 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 spec. vehicles
(B19) No. 2 (+)—Engine ground ():
188
2-7ON-BOARD DIAGNOSTICS II SYSTEM
10. Diagnostic Chart with Trouble Code for LHD Vehicles