1997 SUBARU LEGACY sensor

: Go to step10P5.
: 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
10P5
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.
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10. Diagnostic Chart with Trouble Code for LHD Vehicles

OBD0220
Q: DTC P0136
—REAR OXYGEN SENSOR CIRCUIT
MALFUNCTION—
DTC DETECTING CONDITION:

Two consecutive driving cycles with fault
WIRING DIAGRAM:
B2M1077
CAUTION:
After repair or replacement of faulty parts, conduct
CLEAR MEMORY and INSPECTION MODES.

181
2-7ON-BOARD DIAGNOSTICS II SYSTEM
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.
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2-7ON-BOARD DIAGNOSTICS II SYSTEM
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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2-7ON-BOARD DIAGNOSTICS II SYSTEM
10. Diagnostic Chart with Trouble Code for LHD Vehicles

OBD0229
R: DTC P0139
—REAR OXYGEN SENSOR CIRCUIT SLOW
RESPONSE—
DTC DETECTING CONDITION:

Two consecutive driving cycles with fault
WIRING DIAGRAM:
B2M1077
CAUTION:
After repair or replacement of faulty parts, conduct
CLEAR MEMORY and INSPECTION MODES.

184
2-7ON-BOARD DIAGNOSTICS II SYSTEM
10. Diagnostic Chart with Trouble Code for LHD Vehicles

10R1
CHECK DTC P0136 ON DISPLAY.
: Does the Subaru select monitor or OBD-II
general scan tool indicate DTC P0136?
: Inspect DTC P0136 using“10. Diagnostics Chart
with Trouble Code”.
NOTE:
In this case, it is not necessary to inspect DTC P0139.
: Replace rear oxygen sensor.
185
2-7ON-BOARD DIAGNOSTICS II SYSTEM
10. Diagnostic Chart with Trouble Code for LHD Vehicles

OBD0232
S: DTC P0141
—REAR OXYGEN SENSOR HEATER
CIRCUIT MALFUNCTION—
DTC DETECTING CONDITION:

Two consecutive driving cycles with fault
WIRING DIAGRAM:
B2M1078
CAUTION:
After repair or replacement of faulty parts, conduct
CLEAR MEMORY and INSPECTION MODES.

186
2-7ON-BOARD DIAGNOSTICS II SYSTEM
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.
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2-7ON-BOARD DIAGNOSTICS II SYSTEM
10. Diagnostic Chart with Trouble Code for LHD Vehicles