1996 SUBARU LEGACY Fuel system

H2M1372
AK: DTC P0450
—EVAPORATIVE EMISSION CONTROL
SYSTEM PRESSURE SENSOR
MALFUNCTION (TNKP)—
DTC DETECTING CONDITION:

Immediately at fault recognition
10AK1Connect Subaru Select Monitor or the OBD-II
general scan tool, and read data.

10AK2Check input signal for ECM. (Using voltage
meter and Subaru Select Monitor.)
10AK3Check harness between ECM and fuel tank
pressure sensor connector.
10AK4Check harness between ECM and fuel tank
pressure sensor connector.
CAUTION:
After repair or replacement of faulty parts, conduct
CLEAR MEMORY and INSPECTION MODES.



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

OBD0145A
10AK1CONNECT SUBARU SELECT MONITOR
OR THE OBD-II GENERAL SCAN TOOL,
AND READ DATA.
1) Turn ignition switch to OFF.
2) Remove fuel filler cap.
3) Install fuel filler cap.
4) Connect Subaru Select Monitor or the OBD-II general
scan tool to data link connector.
5) Turn ignition switch to ON and Subaru Select Monitor or
the OBD-II general scan tool switch to ON.
H2M1326
6) Read the data on Subaru Select Monitor or the OBD-II
general scan tool.

Subaru Select Monitor
Designate mode using function key.
Function mode: F43

F43: Display shows pressure signal value sent from fuel
tank pressure sensor.
: Is the value less than2.8 kPa in function
mode F43?
: Go to step10AK2.
: Go to next.
H2M1326
: Is the value more than 2.8 kPa in function
mode F43?
: Go to step10AK4.
: Repair harness and connector.
NOTE:
In this case, repair the following:

Open or short circuit in harness between fuel tank pres-
sure sensor and ECM connector

Poor contact in coupling connectors (B97, and B98 (LHD
only))

Poor contact in fuel tank pressure sensor

Poor contact in ECM connector

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

B2M0535A
10AK2CHECK INPUT SIGNAL FOR ECM.
(USING VOLTAGE METER AND SUBARU
SELECT MONITOR.)
1) Measure voltage between ECM connector and chassis
ground.
: Connector & terminal
(B84) No. 21 (+)—Chassis ground ():
Is the voltage more than 4.5 V?
: Go to next step 2).
: Go to next.
B2M0535A
: 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.
H2M1374B
2) Measure voltage between ECM and chassis ground.
: Connector & terminal
(B84) No. 4 (+)—Chassis ground ():
Is the voltage less than 0.2 V?
: Go to step10AK3.
: Go to next step 3).
H2M1326
3) Read data on Subaru Select Monitor.

Subaru Select Monitor
Designate mode using function key.
Function mode: F43

F43: Display shows pressure signal value sent from fuel
tank pressure sensor.
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2-7ON-BOARD DIAGNOSTICS II SYSTEM
10. Diagnostics Chart with Trouble Code

: Does the value change more than2.8 kPa
by shaking harness and connector of ECM
while monitoring the value with Subaru
select monitor?
: Repair poor contact in ECM connector.
: Go to step10AK3.
B2M0927
10AK3CHECK HARNESS BETWEEN ECM AND
FUEL TANK PRESSURE SENSOR CON-
NECTOR.
1) Turn ignition switch to OFF.
2) Detach right side trunk side trim panel (Sedan) or right
side rear quarter trim panel (Wagon).
3) Remove right side rear quarter trim pocket (Wagon
model only).
4) Detach right side rear quarter insulator (Wagon model
only).
H2M1255B
5) Disconnect connector from fuel tank pressure sensor.
6) Turn ignition switch to ON.
7) Measure voltage between fuel tank pressure sensor
connector and chassis ground.
: Connector & terminal
(R47) No. 3 (+)—Chassis ground ():
Is the voltage more than 4.5 V?
: Go to next step 8).
: Repair harness and connector.
NOTE:
In this case, repair the following:

Open circuit in harness between ECM and fuel tank
pressure sensor connector

Poor contact in coupling connector (B97)
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2-7ON-BOARD DIAGNOSTICS II SYSTEM
10. Diagnostics Chart with Trouble Code

H2M1375B
8) Turn ignition switch to OFF.
9) Disconnect connector from ECM.
10) Measure resistance of harness between ECM and
pressure sensor connector.
: Connector & terminal
(B84) No. 4—(R47) No. 2:
Is the resistance less than 1Ω?
: Go to next.
: Repair harness and connector.
NOTE:
In this case, repair the following:

Open circuit in harness between ECM and fuel tank
pressure sensor connector

Poor contact in coupling connector (B98 (LHD)/B97
(RHD))
H2M1376B
: Connector & terminal
(B84) No. 20—(R47) No. 1:
Is the resistance less than 1Ω?
: Go to next step 11).
: Repair harness and connector.
NOTE:
In this case, repair the following:

Open circuit in harness between ECM and fuel tank
pressure sensor connector

Poor contact in coupling connector (B98 (LHD)/B97
(RHD))
261
2-7ON-BOARD DIAGNOSTICS II SYSTEM
10. Diagnostics Chart with Trouble Code

H2M1257B
11) Measure resistance of harness between fuel tank
pressure sensor connector and chassis ground.
: Connector & terminal
(R47) No. 1—Chassis ground:
Is the resistance more than 500 kΩ?
: Go to next.
: Repair short circuit in harness between ECM and
fuel tank pressure sensor connector.
: Is there poor contact in fuel tank pressure
sensor connector?
: Repair poor contact in fuel tank pressure sensor
connector.
: Replace fuel tank pressure sensor.
B2M0927
10AK4CHECK HARNESS BETWEEN ECM AND
FUEL TANK PRESSURE SENSOR CON-
NECTOR.
1) Turn ignition switch to OFF and Subaru Select Monitor
or the OBD-II general scan tool switch to OFF.
2) Detach right side trunk side trim panel (Sedan) or right
side rear quarter trim panel (Wagon).
3) Remove right side rear quarter trim pocket (Wagon
model only).
4) Detach right side rear quarter insulator (Wagon model
only).
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10. Diagnostics Chart with Trouble Code

H2M1326
5) Disconnect connector from fuel tank pressure sensor.
6) Remove fuel filler cap.
7) Install fuel filler cap.
8) Turn ignition switch to ON and Subaru Select Monitor or
the OBD-II general scan tool switch to ON.
9) Read data on Subaru select monitor or the OBD-II gen-
eral scan tool.

Subaru Select Monitor
Designate mode using function key.
Function mode: F43
: Is the value more than 2.8 kPa in function
mode F43?
: Repair short circuit in harness between ECM and
fuel tank pressure sensor connector.
: Replace fuel tank pressure sensor.

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

WIRING DIAGRAM:

RHD Model
B2M1019
10AL1
CHECK PRESSURE/VACUUM LINE.
: Is there a fault in pressure/vacuum line?
NOTE:
Check the following items.

Disconnection, leakage and clogging of the vacuum
hoses and pipes between fuel tank pressure sensor and
fuel tank

Disconnection, leakage and clogging of air ventilation
hoses and pipes between fuel filler pipe and fuel tank
: Repair or replace hoses and pipes.
: Replace fuel tank pressure sensor.
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2-7ON-BOARD DIAGNOSTICS II SYSTEM
10. Diagnostics Chart with Trouble Code