Subaru 2002 IMPREZA Service Manual page 911

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)
Step
1 CHECK INPUT SIGNAL FOR ECM.
1)Turn the ignition switch to ON.
2)Measure the voltage between ECM connec-
tor 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 the connector from knock sen-
sor.
2)Measure the resistance between knock sen-
sor connector terminal and engine ground.
Terminal
No. 2 — Engine ground:
4 CHECK HARNESS CONNECTOR BETWEEN
ECM AND KNOCK SENSOR.
Measure the 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 the 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.
Check
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)-77
ENGINE (DIAGNOSTICS)
Yes
Go to step 2. Go to step 3.
Repair the poor Replace the ECM.
contact in ECM <Ref. to FU(w/
connector. oOBD)-48, Engine
Control Module.>
Go to step 4. Repair the har-
ness and connec-
tor.
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 5. Replace the knock
sensor. <Ref. to
FU(w/oOBD)-33,
Knock Sensor.>
Go to step 6. Repair the ground
short circuit
between ECM and
knock sensor.
Repair the poor Replace the ECM.
contact in ECM <Ref. to FU(w/
connector. oOBD)-48, Engine
Control Module.>
No