Subaru Legacy 2003 Service Manual page 516

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)
Step
1 CHECK CURRENT DATA.
1) Start engine.
2) Read data of intake air temperature sensor
signal using Subaru Select Monitor or the
OBD-II general scan tool.
Is the measured value less than the speci-
fied value?
NOTE:
•Subaru Select Monitor
For detailed operation procedure, refer to the
"READ CURRENT DATA FOR ENGINE".
<Ref. to EN(H4SO)-32, Subaru Select Moni-
tor.>
•OBD-II general scan tool
For detailed operation procedure, refer to the
OBD-II General Scan Tool Instruction Manual.
2 CHECK HARNESS BETWEEN INTAKE AIR
TEMPERATURE SENSOR AND ECM CON-
NECTOR.
1) Turn ignition switch to OFF.
2) Disconnect connector from intake air tem-
perature sensor.
3) Measure voltage between intake air tem-
perature sensor connector and engine
ground.
Connector & terminal
(E20) No. 1 (+) — Engine ground ( − − − − ):
Does the measured value exceed the spec-
ified value?
3 CHECK HARNESS BETWEEN INTAKE AIR
TEMPERATURE SENSOR AND ECM CON-
NECTOR.
1) Turn ignition switch to ON.
2) Measure voltage between intake air tem-
perature sensor connector and engine
ground.
Connector & terminal
(E20) No. 1 (+) — Engine ground ( − − − − ):
Does the measured value exceed the spec-
ified value?
4 CHECK HARNESS BETWEEN INTAKE AIR
TEMPERATURE SENSOR AND ECM CON-
NECTOR.
Measure voltage between intake air tempera-
ture and pressure sensor connector and
engine ground.
Connector & terminal
(E20) No. 1 (+) — Engine ground ( − − − − ):
Does the measured value exceed the specified
value?
Value
−40°C (−40°F)
10 V
10 V
3 V
EN(H4SO)-119
ENGINE (DIAGNOSTICS)
Yes
Go to step 2. Repair poor con-
tact.
NOTE:
In this case, repair
the following:
• Poor contact in
intake air tempera-
ture sensor
• Poor contact in
ECM
• Poor contact in
coupling connector
• Poor contact in
joint connector
Repair battery Go to step 3.
short circuit in har-
ness between
intake air tempera-
ture sensor and
ECM connector.
Repair battery Go to step 4.
short circuit in har-
ness between
intake air tempera-
ture sensor and
ECM connector.
Go to step 5. Repair harness
and connector.
NOTE:
In this case, repair
the following:
• Open circuit in
harness between
intake air tempera-
ture sensor and
ECM connector
• Poor contact in
intake air tempera-
ture sensor
• Poor contact in
ECM
• Poor contact in
coupling connector
• Poor contact in
joint connector
No