1996 SUBARU LEGACY check engine

OBD0618A
10F2CHECK HARNESS BETWEEN ENGINE
COOLANT TEMPERATURE SENSOR AND
ECM CONNECTOR.
1) Turn ignition switch to OFF.
2) Remove idle air control solenoid valve by-pass air hose.
3) Disconnect connector from engine coolant temperature
sensor.
OBD0145A
4) Connect Subaru Select Monitor or the OBD-II general
scan tool to data link connector.
5) Turn ignition switch and Subaru Select Monitor or
OBD-II general scan tool switch to ON.
B2M0479
6) 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 the value less than40°Cor40°Fin
function mode F04?
: Replace engine coolant temperature sensor.
: Repair short circuit in harness between engine
coolant temperature sensor and 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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10. Diagnostics Chart with Trouble Code

OBD0618A
10F3CHECK HARNESS BETWEEN ENGINE
COOLANT TEMPERATURE SENSOR AND
ECM CONNECTOR.
1) Turn ignition switch to OFF.
2) Remove idle air control solenoid valve by-pass air hose.
3) Disconnect connector from engine coolant temperature
sensor.
4) Turn ignition switch to ON.
OBD0696A
5) Measure voltage between engine coolant temperature
sensor connector and engine ground.
: Connector & terminal
(E8) No. 1 (+)—Engine ground ():
Is the voltage more than 4 V?
: Go to next step 6).
: Repair harness and connector.
NOTE:
In this case, repair the following:

Open circuit in harness between ECM and engine cool-
ant temperature sensor connector

Poor contact in engine coolant temperature sensor con-
nector

Poor contact in ECM connector

Poor contact in coupling connector (B21)
OBD0697A
6) Turn ignition switch to OFF.
7) Measure resistance of harness between engine coolant
temperature sensor connector and engine ground.
: Connector & terminal
(E8) No. 2—Engine ground:
Is the resistance less than 5Ω?
: Replace engine coolant temperature sensor.
: Repair harness and connector.
NOTE:
In this case, repair the following:

Open circuit in harness between ECM and engine cool-
ant temperature sensor connector

Poor contact in engine coolant temperature sensor con-
nector

Poor contact in ECM connector

Poor contact in coupling connector (B21)
150
2-7ON-BOARD DIAGNOSTICS II SYSTEM
10. Diagnostics Chart with Trouble Code

OBD0181
G: DTC P0120
—THROTTLE POSITION SENSOR CIRCUIT
MALFUNCTION (THV)—
DTC DETECTING CONDITION:

Immediately at fault recognition
TROUBLE SYMPTOM:

Erroneous idling

Engine stalls.

Poor driving performance
10G1Connect Subaru Select Monitor or the OBD-II
general scan tool and read data.

10G2Check input signal for ECM. (Using voltage
meter and Subaru select monitor.)
10G3Check harness between ECM and throttle
position sensor connector.
10G4Check harness between throttle position
sensor and body connector.
CAUTION:
After repair or replacement of faulty parts, conduct
CLEAR MEMORY and INSPECTION MODES.



151
2-7ON-BOARD DIAGNOSTICS II SYSTEM
10. Diagnostics Chart with Trouble Code

OBD0700A
10G3CHECK HARNESS BETWEEN ECM AND
THROTTLE POSITION SENSOR CON-
NECTOR.
1) Turn ignition switch to OFF.
2) Disconnect connectors from throttle position sensor.
3) Turn ignition switch to ON.
4) Measure voltage between throttle position sensor con-
nector and engine ground.
: Connector & terminal
(E13) No. 3 (+)—Engine ground ():
Is the voltage more than 4.5 V?
: Go to next step 5).
: Repair harness and connector.
NOTE:
In this case, repair the following:

Open circuit in harness between throttle position sensor
and ECM connector

Poor contact in throttle position sensor connector

Poor contact in ECM connector

Poor contact in coupling connector (B21)
B2M0543A
5) Turn ignition switch to OFF.
6) Measure resistance of harness between ECM connec-
tor and throttle position sensor connector.
: Connector & terminal
(B84) No. 6—(E13) No. 2:
Is the resistance less than 1Ω?
: Go to next step 7).
: Repair harness and connector.
NOTE:
In this case, repair the following:

Open circuit in harness between throttle position sensor
and ECM connector

Poor contact in ECM connector

Poor contact in throttle position sensor connector

Poor contact in coupling connector (B21)
155
2-7ON-BOARD DIAGNOSTICS II SYSTEM
10. Diagnostics Chart with Trouble Code

OBD0702A
7) Measure resistance of harness between throttle posi-
tion sensor connector and engine ground.
: Connector & terminal
(E13) No. 2—Engine ground:
Is the resistance less than 10Ω?
: Repair short circuit in harness between throttle
position sensor and ECM connector.
: Go to next.
: Is there poor contact in throttle position
sensor connector?
: Repair poor contact in throttle position sensor
connector.
: Replace throttle position sensor.
OBD0703A
10G4CHECK HARNESS BETWEEN THROTTLE
POSITION SENSOR AND BODY CON-
NECTOR.
1) Turn ignition switch to OFF.
2) Disconnect connector from throttle position sensor.
3) Measure resistance of harness between throttle posi-
tion sensor connector and engine ground.
: Connector & terminal
(E13) No. 1—Engine ground:
Is the resistance less than 5Ω?
: Go to next step 4).
: Repair open circuit in harness between throttle
position sensor and ECM connector.
OBD0704A
4) Turn ignition switch to ON.
5) Measure voltage between throttle position sensor con-
nector and engine ground.
: Connector & terminal
(E13) No. 2 (+)—Engine ground ():
Is the voltage more than 4.9 V?
: Repair short circuit in harness between throttle
position sensor and ECM connector.
: Replace throttle position sensor.
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2-7ON-BOARD DIAGNOSTICS II SYSTEM
10. Diagnostics Chart with Trouble Code

OBD0189
H: DTC P0121
—THROTTLE POSITION SENSOR CIRCUIT
RANGE/PERFORMANCE PROBLEM
(TH
—R)—
DTC DETECTING CONDITION:

Two consecutive trips with fault
TROUBLE SYMPTOM:

Erroneous idling

Engine stalls.

Poor driving performance
10H1Check DTC P0120 on display.
CAUTION:
After repair or replacement of faulty parts, conduct
CLEAR MEMORY and INSPECTION MODES.

WIRING DIAGRAM:
B2M0540
157
2-7ON-BOARD DIAGNOSTICS II SYSTEM
10. Diagnostics Chart with Trouble Code

OBD0191
I: DTC P0125
—INSUFFICIENT COOLANT TEMPERATURE
FOR CLOSED LOOP FUEL CONTROL
(TW
—CL)—
DTC DETECTING CONDITION:

Two consecutive trips with fault
TROUBLE SYMPTOM:

Engine would not return to idling.
10I1Check DTC P0115 on display.
CAUTION:
After repair or replacement of faulty parts, conduct
CLEAR MEMORY and INSPECTION MODES.

WIRING DIAGRAM:
B2M0539
159
2-7ON-BOARD DIAGNOSTICS II SYSTEM
10. Diagnostics Chart with Trouble Code

10I1
CHECK DTC P0115 ON DISPLAY.
: Does the Subaru select monitor or OBD-II
general scan tool indicate DTC P0115?
: Inspect DTC P0115 using“10. Diagnostics Chart
with Trouble Code 2-7 [T1000]”.
NOTE:
In this case, it is not necessary to inspect DTC P0125.
: Replace engine coolant temperature sensor.
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2-7ON-BOARD DIAGNOSTICS II SYSTEM
10. Diagnostics Chart with Trouble Code