Subaru Legacy 2003 Service Manual page 1934

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)
Step
1 CHECK CURRENT DATA.
1) Start the engine.
2) Read the data of intake air temperature
sensor signal using Subaru Select Monitor.
Is the measured value less than the speci-
fied value?
NOTE:
For detailed operation procedure, refer to the
"READ CURRENT DATA FOR ENGINE". <Ref.
to EN(H4DOSTC)-26, Subaru Select Monitor.>
2 CHECK HARNESS BETWEEN MASS AIR
FLOW AND INTAKE AIR TEMPERATURE
SENSOR AND ECM CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from mass air
flow and intake air temperature sensor.
3) Measure the voltage between mass air flow
and intake air temperature sensor connec-
tor and engine ground.
Connector & terminal
(B3) No. 2 (+) — Engine ground ( − − − − ):
Does the measured value exceed the spec-
ified value?
3 CHECK HARNESS BETWEEN MASS AIR
FLOW AND INTAKE AIR TEMPERATURE
SENSOR AND ECM CONNECTOR.
1) Turn the ignition switch to ON.
2) Measure the voltage between mass air flow
and intake air temperature sensor connec-
tor and engine ground.
Connector & terminal
(B3) No. 2 (+) — Engine ground ( − − − − ):
Does the measured value exceed the spec-
ified value?
4 CHECK HARNESS BETWEEN MASS AIR
FLOW AND INTAKE AIR TEMPERATURE
SENSOR AND ECM CONNECTOR.
Measure the voltage between mass air flow
and intake air temperature sensor and pres-
sure sensor connector and engine ground.
Connector & terminal
(B3) No. 2 (+) — Engine ground ( − − − − ):
Does the measured value exceed the specified
value?
Value
−36°C (−97°F)
10 V
10 V
4 V
EN(H4DOSTC)-95
ENGINE (DIAGNOSTICS)
Yes
Go to step 2. Repair the poor
contact.
NOTE:
In this case, repair
the following:
• Poor contact in
mass air flow and
intake air tempera-
ture sensor
• Poor contact in
ECM
• Poor contact in
joint connector
Repair the battery Go to step 3.
short circuit in har-
ness between
mass air flow and
intake air tempera-
ture sensor and
ECM connector.
Repair the battery Go to step 4.
short circuit in har-
ness between
mass air flow and
intake air tempera-
ture sensor and
ECM connector.
Go to step 5. Repair the har-
ness and connec-
tor.
NOTE:
In this case, repair
the following:
• Open circuit in
harness between
mass air flow and
intake air tempera-
ture sensor and
ECM connector
• Poor contact in
mass air flow and
intake air tempera-
ture sensor
• Poor contact in
ECM
• Poor contact in
joint connector
No