Subaru Forester 2004 Service Manual page 135

Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTIC)
Step
1 CHECK HARNESS BETWEEN KNOCK SEN-
SOR AND ECM CONNECTOR.
Measure the resistance of harness between
ECM connector and chassis ground.
Connector & terminal
(B136) No. 25 — Chassis ground:
2 CHECK KNOCK SENSOR.
1) Disconnect the connector from knock sensor.
2) Measure the resistance between knock
sensor connector terminal and engine ground.
Terminals
No. 2 — Engine ground:
3 CHECK INPUT SIGNAL FROM 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. 25 (+) — Chassis ground (
Check
Is the resistance less than 400
kΩ?
Is the resistance less than 400
kΩ?
Is the voltage more than 2 V?
−
):
EN(H4DOTC 2.5)-134
Yes
Go to step 2. Go to step 3.
Replace the knock Repair ground short
sensor. <Ref. to circuit in harness
FU(H4DOTC 2.5)- between knock sen-
29, Knock Sen- sor connector and
sor.> ECM connector.
NOTE:
The harness be-
tween both con-
nectors are
shielded. Repair
short circuit in har-
ness covered with
shield.
Even if the mal- Repair the poor
function indicator contact in ECM
light illuminates, connector.
the circuit has
returned to a nor-
mal condition at
this time. (How-
ever, the possibility
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
No