Subaru 2002 IMPREZA Service Manual page 555

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)
Step
1 CHECK CURRENT DATA.
1)Start the engine.
2)Read the data of intake air temperature sen-
sor signal using Subaru Select Monitor or
OBD-II general scan tool.
NOTE:
•Subaru Select Monitor
For detailed operation procedure, refer to the
"READ CURRENT DATA FOR ENGINE".
<Ref. to EN-34, Subaru Select Monitor.>
•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 AND PRESSURE SENSOR
AND ECM CONNECTOR.
1)Turn the ignition switch to OFF.
2)Disconnect the connector from intake air
temperature and pressure sensor.
3)Measure the voltage between intake air tem-
perature and pressure sensor connector and
engine ground.
Connector & terminal
(E20) No. 2 (+) — Engine ground ( − − − − ):
3 CHECK HARNESS BETWEEN INTAKE AIR
TEMPERATURE AND PRESSURE SENSOR
AND ECM CONNECTOR.
1)Turn the ignition switch to ON.
2)Measure the voltage between intake air tem-
perature and pressure sensor connector and
engine ground.
Connector & terminal
(E20) No. 2 (+) — Engine ground ( − − − − ):
Check
Is the value less than −40°C
(−40°F)?
Is the voltage more than 10 V? Repair the battery
Is the voltage more than 10 V? Repair the battery
EN-123
ENGINE (DIAGNOSTICS)
Yes
Go to step 2. Repair the poor
contact.
NOTE:
In this case, repair
the following:
• Poor contact in
intake air tempera-
ture and pressure
sensor
• Poor contact in
ECM
• Poor contact in
coupling connector
(B21)
• Poor contact in
joint connector
(B83), (B122)
Go to step 3.
short circuit in har-
ness between
intake air tempera-
ture and pressure
sensor and ECM
connector.
Go to step 4.
short circuit in har-
ness between
intake air tempera-
ture and pressure
sensor and ECM
connector.
No