Subaru Legacy 2002 Service Manual page 890

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)
No.
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 (–):
2 CHECK POOR CONTACT.
Check 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:
4 CHECK HARNESS CONNECTOR
BETWEEN ECM AND KNOCK SENSOR.
Measure resistance of harness connector
between ECM and knock sensor.
Connector & terminal
(E14) No. 2 — Chassis ground:
5 CHECK HARNESS CONNECTOR
BETWEEN ECM AND KNOCK SENSOR.
Measure resistance of harness of harness
connector between ECM connector and knock
sensor.
Connector & terminal
(B136) No. 4 — Chassis ground:
6 CHECK POOR CONTACT.
Check poor contact in ECM connector.
Step
Is the voltage more than 3
V?
Is there poor contact in
ECM connector?
Is the resistance between
530 kΩ and 590 kΩ?
Is the resistance less than
1 Ω?
Is the resistance more than
1 MΩ?
Is there poor contact in
ECM connector?
EN(w/oOBD)-79
Check Yes
Go to step 2.
Repair poor con-
tact in ECM con-
nector.
Go to step 4.
Go to step 5.
Go to step 6.
Repair poor con-
tact in ECM con-
nector.
Engine (Diagnostics)
No
Go to step 3.
Replace ECM.
<Ref. to FU(w/
oOBD)-45, Engine
Control Module.>
Repair harness
and connector.
NOTE:
In this case,
repair the follow-
ing:
¼ Open circuit in
harness between
knock sensor and
ECM connector
¼ Poor contact in
knock sensor con-
nector
¼ Poor contact in
coupling connec-
tor (B21)
Replace knock
sensor. <Ref. to
FU(w/oOBD)-30,
Knock Sensor.>
Repair ground
short circuit
between ECM
and knock sensor.
Replace ECM.
<Ref. to FU(w/
oOBD)-45, Engine
Control Module.>