1997 SUBARU LEGACY sensor

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 ():
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Except 2200 cc California spec. vehicles
(T6) No. 2 (+)—Chassis ground ():
Is the voltage more than 10 V?
: Go to step10S5.
: 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 spec. vehicles)
OBD0706
10S5
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.
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6) After connecting pressure regulator vacuum hose, mea-
sure fuel pressure.
: Is fuel pressure between 157 and 206 kPa
(1.6—2.1 kg/cm2,23—30 psi)?
: Go to step10T4.
: Repair the following items.
Fuel pressure too high
Faulty pressure regulator

Clogged fuel return line or bent
hose
Fuel pressure too low
Faulty pressure regulator

Improper fuel pump discharge

Clogged fuel supply line
WARNING:
Before removing fuel pressure gauge, release fuel
pressure.
NOTE:

If fuel pressure does not increase, squeeze fuel return
hose 2 to 3 times, then measure fuel pressure again.

If out of specification as measured at this step, check or
replace pressure regulator and pressure regulator vacuum
hose.
OBD0145A
10T4CHECK ENGINE COOLANT TEMPERA-
TURE SENSOR.
DTC P0117 [T10I0].>
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 completely.
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B2M0479
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: F04

F04: Water temperature is indicated in“°C”and“°F”.
: Is temperature greater than 60°Cor140°Fin
function mode F04?
: Go to step10T5.
: 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.
OBD0145A
10T5
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).
4) Place the selector lever in“N”or“P”position.
5) Turn A/C switch to OFF.
6) Turn all accessory switches to OFF.
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B2M0481
7) Read data on Subaru Select Monitor or OBD-II general
scan tool.

Subaru Select Monitor
Designate mode using function key.
Function mode: F06

F06: Mass air flow and voltage input from mass air flow
sensor are shown on display.
: Is the voltage in function mode F06 within
the specifications shown in the following
table?
Model Engine speed Specified value
2200 ccIdling 1.7—3.3 (g/sec)
2,500 rpm 7.1—14.2 (g/sec)
2500 ccIdling 2.2—4.2 (g/sec)
2,500 rpm 8.6—14.5 (g/sec)
: Contact with SOA service.
NOTE:
Inspection by DTM is required, because probable cause is
deterioration of multiple parts.
: Replace mass air flow sensor.

OBD-II general scan tool
For detailed operation procedures, refer to the OBD-II Gen-
eral Scan Tool Instruction Manual.
194
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H2M1350
U: DTC P0181
—FUEL TEMPERATURE SENSOR A CIRCUIT
RANGE/PERFORMANCE PROBLEM—
DTC DETECTING CONDITION:

Two consecutive driving cycles with fault
WIRING DIAGRAM:
B2M0916
CAUTION:
After repair or replacement of faulty parts, conduct
CLEAR MEMORY and INSPECTION MODES.

195
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10U1CHECK DTC P0182 OR P0183 ON DIS-
PLAY.
: Does the Subaru select monitor or OBD-II
general scan tool indicate DTC P0182 or
P0183?
: Inspect DTC P0182 or P0183 using“10. Diagnos-
tics Chart with Trouble Code”. [T10A0].>
NOTE:
In this case, it is not necessary to inspect DTC P0181.
: Replace fuel temperature sensor.
196
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10. Diagnostic Chart with Trouble Code for LHD Vehicles

B2M1079
V: DTC P0182
—FUEL TEMPERATURE SENSOR A CIRCUIT
LOW INPUT—
DTC DETECTING CONDITION:

Immediately at fault recognition
WIRING DIAGRAM:
B2M0916
CAUTION:
After repair or replacement of faulty parts, conduct
CLEAR MEMORY and INSPECTION MODES.

197
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10. Diagnostic Chart with Trouble Code for LHD Vehicles