Subaru 2009 IMPREZA Service Manual page 1333

Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step
1 CHECK CURRENT DATA.
1) Start the engine.
2) Read the data of air flow sensor signal using
Subaru Select Monitor or general scan tool.
NOTE:
• Subaru Select Monitor
For detailed operation procedures, refer to
"READ CURRENT DATA FOR ENGINE". <Ref.
to EN(H4DOTC)(diag)-34, Subaru Select Moni-
tor.>
• General scan tool
For detailed operation procedures, refer to the
general scan tool operation manual.
2 CHECK HARNESS BETWEEN ECM AND
MASS AIR FLOW AND INTAKE AIR TEM-
PERATURE SENSOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from the mass
air flow and intake air temperature sensor.
3) Start the engine.
4) Read the data of air flow sensor signal using
Subaru Select Monitor or general scan tool.
NOTE:
• Subaru Select Monitor
For detailed operation procedures, refer to
"READ CURRENT DATA FOR ENGINE". <Ref.
to EN(H4DOTC)(diag)-34, Subaru Select Moni-
tor.>
• General scan tool
For detailed operation procedures, refer to the
general scan tool operation manual.
3 CHECK HARNESS BETWEEN ECM AND
MASS AIR FLOW AND INTAKE AIR TEM-
PERATURE SENSOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Measure the resistance of harness between
mass air flow and intake air temperature sensor
connector and engine ground.
Connector & terminal
(B3) No. 4 — Engine ground:
4 CHECK POOR CONTACT.
Check for poor contact of mass air flow and
intake air temperature sensor connector.
Check
Is the voltage 5 V or more?
Is the voltage 5 V or more?
Is the resistance less than 5 ? Go to step 4.
Is there poor contact of mass
air flow and intake air tempera-
ture sensor connector?
EN(H4DOTC)(diag)-112
Yes No
Go to step 2. Even if DTC is
detected, the cir-
cuit has returned to
a normal condition
at this time. Repro-
duce the failure,
and then perform
the diagnosis
again.
NOTE:
In this case, tem-
porary poor con-
tact of connector
may be the cause.
Repair the short Go to step 3.
circuit of harness
to power supply
between ECM and
mass air flow and
intake air tempera-
ture sensor con-
nector.
Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
• Open circuit in
harness between
ECM and mass air
flow and intake air
temperature sen-
sor connector.
• Poor contact of
ECM connector
Repair the poor Replace the mass
contact of mass air air flow and intake
flow and intake air air temperature
temperature sen- sensor. <Ref. to
sor connector. FU(H4DOTC)-39,
Mass Air Flow and
Intake Air Temper-
ature Sensor.>