Subaru 2004 LEGACY Service Manual page 51

Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step
1 CHECK CURRENT DATA.
1) Start the engine.
2) Read the data of mass air flow and intake
air temperature sensor signal using Subaru
Select Monitor or OBD-II general scan tool.
NOTE:
• Subaru Select Monitor
For detailed operation procedures, refer to the
"READ CURRENT DATA SHOWN ON DIS-
PLAY FOR ENGINE". <Ref. to
EN(H6DO)(diag)-25, Subaru Select Monitor.>
• OBD-II general scan tool
For detailed operation procedures, refer to the
OBD-II General Scan Tool Operation Manual.
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 mass air flow and
intake air temperature sensor.
3) Turn the ignition switch to ON.
4) Read the data of mass air flow and intake
air temperature sensor signal using Subaru
Select Monitor.
NOTE:
For detailed operation procedures, refer to the
"READ CURRENT DATA SHOWN ON DIS-
PLAY FOR ENGINE". <Ref. to EN(H6DO)(di-
ag)-25, Subaru Select Monitor.>
Check
Is the intake air temperature
more than 120°C (248°F)?
Is the intake air temperature
less than −40°C (−40°F)?
EN(H6DO)(diag)-120
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
coupling connector
• Poor contact in
joint connector
Replace the mass Repair the ground
air flow and intake short circuit in har-
air temperature ness between
sensor. <Ref. to mass air flow and
FU(H6DO)-24, intake air tempera-
Mass Air Flow and ture sensor and
Intake Air Temper- ECM connector.
ature Sensor.>
No