Subaru Legacy 2003 Service Manual page 891

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)
ENGINE (DIAGNOSTICS)
1 CHECK INPUT SIGNAL FOR ECM.
1) Turn ignition switch to ON.
2) Measure voltage between ECM connector
and chassis ground.
Connector & terminal
(B136) No. 4 (+) — Chassis ground (–):
Does the measured value exceed the spec-
ified value?
2 CHECK POOR CONTACT.
Check poor contact in ECM connector.
Is there poor contact in ECM connector?
3 CHECK KNOCK SENSOR.
1) Disconnect connector from knock sensor.
2) Measure resistance between knock sensor
connector terminal and engine ground.
Terminal
No. 2 — Engine ground:
Is the measured value within the specified
value?
4 CHECK HARNESS CONNECTOR BETWEEN
ECM AND KNOCK SENSOR.
1) Remove ECM connector.
2) Measure resistance of harness connector
between ECM and knock sensor.
Connector & terminal
(E14) No. 2 — (B136) No. 4:
Is the measured value less than the speci-
fied value?
5 CHECK HARNESS CONNECTOR BETWEEN
ECM AND KNOCK SENSOR.
Measure resistance of harness of harness con-
nector between ECM connector and knock
sensor.
Connector & terminal
(B136) No. 4 — Chassis ground:
Does the measured value exceed the specified
value?
6 CHECK POOR CONTACT.
Check poor contact in ECM connector.
Is there poor contact in ECM connector?
Step
EN(H4SOw/oOBD)-72
Value
3 V
There is poor contact.
530 kΩ — 590 kΩ
1 Ω
1 MΩ
There is poor contact.
Yes
Go to step 2. Go to step 3.
Repair poor con- Replace ECM.
tact in ECM con- <Ref. to
nector. FU(H4SOw/
oOBD)-42, Engine
Control Module.>
Go to step 4. Replace knock
sensor. <Ref. to
FU(w/oOBD)-,
Knock Sensor.>
Go to step 5. Repair harness
and connector.
NOTE:
In this case, repair
the following:
• Open circuit in
harness between
knock sensor and
ECM connector
• Poor contact in
knock sensor con-
nector
• Poor contact in
coupling connector
(B21)
Go to step 6. Repair ground
short circuit
between ECM and
knock sensor.
Repair poor con- Replace ECM.
tact in ECM con- <Ref. to
nector. FU(H4SOw/
oOBD)-42, Engine
Control Module.>
No