Subaru 2009 IMPREZA Service Manual page 606

Diagnostic Procedure with Diagnostic Trouble Code (DTC)
Step
1 CHECK HARNESS BETWEEN ECM AND
KNOCK SENSOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM.
3) Measure the resistance between ECM con-
nectors.
Connector & terminal
(B134) No. 15 — (B134) No. 29:
2 CHECK KNOCK SENSOR.
1) Disconnect the connector from knock sen-
sor.
2) Measure the resistance between knock
sensor terminals.
Terminals
No. 1 — No. 2:
3 CHECK INPUT SIGNAL OF ECM.
1) Connect the connector to ECM.
2) Turn the ignition switch to ON.
3) Measure the voltage between ECM and
chassis ground.
Connector & terminal
(B134) No. 15 (+) — Chassis ground (–):
Check
Is the resistance less than
500 k ?
Is the resistance less than
500 k ?
Is the voltage 2 V or more?
EN(H4SO)(diag)-189
ENGINE (DIAGNOSTICS)
Yes No
Go to step 2. Go to step 3.
Replace the knock Repair the short
sensor. <Ref. to circuit to ground in
FU(H4SO)-30, harness between
Knock Sensor.> ECM and knock
sensor connector.
NOTE:
The harness be-
tween both con-
nectors
shielded. Remove
the shield and re-
pair the short cir-
cuit of harness.
Even if DTC is Repair the poor
detected, the cir- contact of ECM
cuit has returned to connector.
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.
are