Subaru Legacy 2002 Service Manual page 3361

DIAGNOSTICS CHART WITH TROUBLE CODE (DTC)
Immobilizer (Diagnostics)
No.
1 CHECK POWER SUPPLY CIRCUIT OF IMM
ECM.
1) Turn ignition switch OFF.
2) Disconnect harness connector from IMM
ECM.
3) Measure voltage between IMM ECM har-
ness connector terminal and chassis ground.
Connector & terminal
(B141) No. 10, No.11 (+) — Chassis
ground (−):
2 CHECK POWER SUPPLY CIRCUIT OF IMM
ECM.
1) Turn ignition switch ON. (Engine OFF.)
2) Measure voltage between IMM ECM har-
ness connector terminal and chassis ground.
Connector & terminal
(B141) No. 12 (+) — Chassis ground
(−):
3 CHECK GROUND CIRCUIT OF IMM ECM.
1) Turn ignition switch OFF.
2) Measure resistance between IMM ECM
harness connector terminal and chassis
ground.
Connector & terminal
(B141) No. 2, No.3 (+) — Chassis
ground (−):
4 CHECK HARNESS BETWEEN IMM ECM
AND ECM.
1) Disconnect harness connector from ECM
and IMM ECM.
2) Measure resistance between IMM ECM
harness connector terminal and ECM harness
connector terminal.
Connector & terminal
4-cylinder engine model:
(B141) No. 1 — (B135) No. 22:
6-cylinder engine model:
(B141) No. 1 — (B135) No. 5:
5 CHECK HARNESS BETWEEN IMM ECM
AND ECM.
Measure resistance between IMM ECM har-
ness connector terminal and ECM harness
connector terminal.
Connector & terminal
4-cylinder engine model:
(B141) No. 6 — (B135) No. 23:
6-cylinder engine model:
(B141) No. 6 — (B135) No. 14:
6 CHECK HARNESS OF COMMUNICATION
LINE.
1) Turn ignition switch ON. (Engine OFF.)
2) Measure voltage between IMM ECM har-
ness connector terminal and chassis ground.
Connector & terminal
(B141) No. 1, No.6 (+) — Chassis
ground (−):
Step
Is the voltage more than 10
V?
Is the voltage more than 10
V?
Is the resistance less than
10 Ω?
Is the resistance less than
10 Ω?
Is the resistance less than
10 Ω?
Is the voltage 0 V?
IM-16
Check Yes
Go to step 2.
Go to step 3.
Go to step 4.
Go to step 5.
Go to step 6.
Go to step 7.
No
Check harness for
open or short
between IMM
ECM and fuse.
Check harness for
open or short
between IMM
ECM and ignition
switch.
Repair open cir-
cuit of IMM ECM
ground circuit.
Repair open cir-
cuit of harness
between IMM
ECM and ECM.
Repair open cir-
cuit of harness
between IMM
ECM and ECM.
Repair harness
between IMM
ECM and ECM,
because there is
short circuit in
battery voltage
line or ignition
switch "ON" line.