Subaru 2002 IMPREZA Service Manual page 601

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)
Step
2 CHECK KNOCK SENSOR.
1)Disconnect the connector from knock sen-
sor.
2)Measure the resistance between knock sen-
sor connector terminal and engine ground.
Terminal
No. 2 — Engine ground:
3 CHECK INPUT SIGNAL FOR ECM.
1)Connect the connectors to ECM and knock
sensor.
2)Turn the ignition switch to ON.
3)Measure the voltage between ECM and
chassis ground.
Connector & terminal
(B136) No. 4 (+) — Chassis ground ( − − − − ):
Check
Is the resistance less than 400
kΩ?
Is the voltage more than 2 V?
EN-169
ENGINE (DIAGNOSTICS)
Yes
Replace the knock Repair the ground
sensor. <Ref. to short circuit in har-
FU-34, Knock ness between
Sensor.> knock sensor con-
nector and ECM
connector.
NOTE:
The harness be-
tween both con-
nectors
shielded.
the short circuit of
harness
with shield.
Even if MIL lights Repair the poor
up, the circuit has contact in ECM
returned to a nor- connector.
mal condition at
this time. (How-
ever, the possibil-
ity of poor contact
still remains.)
NOTE:
In this case, repair
the following:
• Poor contact in
knock sensor con-
nector
• Poor contact in
ECM connector
• Poor contact in
coupling connector
(B21)
No
is
Repair
together