Subaru IMPREZA GD 2007 Series Manual page 226

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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 gen-
eral scan tool.
NOTE:
• Subaru Select Monitor
For detailed operation procedures, refer to
"READ CURRENT DATA FOR ENGINE". <Ref.
to EN(H4SO)(diag)-32, Subaru Select Monitor.>
• General scan tool
For detailed operation procedure, refer to the
general scan tool operation manual.
2 CHECK POOR CONTACT.
Repair any poor contact between the ECM and
the mass air flow and intake air temperature
sensor connectors.
3 CHECK HARNESS BETWEEN ECM AND
THE MASS AIR FLOW AND INTAKE AIR
TEMPERATURE SENSOR CONNECTORS.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from the ECM
and the mass air flow and intake air temperature
sensor.
3) Measure the resistance of harness between
ECM and the mass air flow and intake air tem-
perature sensor connectors.
Connector & terminal
(B135) No. 30 — (B3) No. 5:
4 CHECK HARNESS BETWEEN ECM AND
THE MASS AIR FLOW AND INTAKE AIR
TEMPERATURE SENSOR CONNECTORS.
1) Connect all connectors.
2) Turn the ignition switch to ON.
3) Measure the voltage between ECM and
chassis ground.
Connector & terminal
(B135) No. 18 (+) — Chassis ground (–):
Check
Is the intake air temperature
less than –40°C (–40°F) ?
Is there poor contact in the
ECM or the mass air flow and
intake air temperature sensor
connectors?
Is the resistance less than 1 Ω? Go to step 4.
Is the voltage 5 V or more?
EN(H4SO)(diag)-117
ENGINE (DIAGNOSTICS)
Yes No
Go to step 2. Even if the malfunc-
tion indicator light
illuminates, the cir-
cuit has returned to
a normal condition
at this time. Repro-
duce the fault con-
dition, and
reperform the
check.
NOTE:
In this case, there
may be a tempo-
rary connector
contact failure.
Repair any poor Go to step 3.
contact between
the ECM and the
mass air flow and
intake air tempera-
ture sensor con-
nectors.
Repair the open
circuit of harness
between the ECM
and mass air flow
and intake air tem-
perature sensor
connectors.
Repair the short Replace the mass
circuit to power in air flow and intake
the harness air temperature
between the ECM sensor. <Ref. to
and the mass air FU(H4SO)-28,
flow and intake air Mass Air Flow and
temperature sen- Intake Air Temper-
sor connectors. ature Sensor.>