Subaru 2009 IMPREZA Service Manual page 553

Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step
1 CHECK CURRENT DATA.
1) Start the engine.
2) Read the data of engine coolant tempera-
ture 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(H4SO)(diag)-34, Subaru Select Moni-
tor.>
• General scan tool
For detailed operation procedures, refer to the
general scan tool operation manual.
2 CHECK POOR CONTACT.
Check for poor contact of ECM and engine cool-
ant temperature sensor connector.
3 CHECK HARNESS BETWEEN ECM AND EN-
GINE COOLANT TEMPERATURE SENSOR
CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM and
engine coolant temperature sensor.
3) Measure the resistance of harness between
ECM and engine coolant temperature sensor
connector.
Connector & terminal
(B134) No. 34 — (E8) No. 2:
(B134) No. 29 — (E8) No. 1:
4 CHECK HARNESS BETWEEN ECM AND EN-
GINE COOLANT TEMPERATURE SENSOR
CONNECTOR.
1) Connect all connectors.
2) Turn the ignition switch to ON.
3) Measure the voltage between ECM and
chassis ground.
Connector & terminal
(B134) No. 34 (+) — Chassis ground (–):
Check
Is the engine coolant tempera-
ture less than –40°C (–40°F) ?
Is there poor contact of ECM or
engine coolant temperature
sensor connector?
Is the resistance less than 1 ? Go to step 4.
Is the voltage 5 V or more?
EN(H4SO)(diag)-136
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 poor Go to step 3.
contact of ECM or
engine coolant
temperature sen-
sor connector.
Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
• Open circuit in
harness between
ECM and engine
coolant
ture sensor con-
nector
• Poor contact of
coupling connector
Repair the short Replace the
circuit to power in engine coolant
harness between temperature sen-
ECM and engine sor. <Ref. to
coolant tempera- FU(H4SO)-25,
ture sensor con- Engine Coolant
nector. Temperature Sen-
sor.>
tempera-