Subaru Legacy III (2000-2003 year). Manual — part 1009

IM-20

IMMOBILIZER (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH TROUBLE CODE (DTC)

Step

Value

Yes

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 (

−−−−

):

Does the measured value exceed the spec-
ified value?

10 V

Go to step 2.

Check harness for
open or short
between IMM
ECM and fuse.

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 (

−−−−

):

Does the measured value exceed the spec-
ified value?

10 V

Go to step 3.

Check harness for
open or short
between IMM
ECM and ignition
switch.

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:

Is the measured value less than the speci-
fied value?

10

Ω

Go to step 4.

Repair open circuit
of IMM ECM
ground circuit.

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 har-
ness connector terminal.

Connector & terminal

H4 non-TURBO without OBD model

(B141) No. 1 — (B135) No. 22:

H4 Non-TURBO with OBD model

(B141) No. 1 — (B137) No. 18:

H6 and H4 TURBO models

(B141) No. 1 — (B135) No. 5:

Is the measured value less than the speci-
fied value?

10

Ω

Go to step 5.

Repair open circuit
of harness
between IMM
ECM and ECM.

IM-21

IMMOBILIZER (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH TROUBLE CODE (DTC)

5

CHECK HARNESS BETWEEN IMM ECM
AND ECM.
Measure resistance between IMM ECM har-
ness connector terminal and ECM harness
connector terminal.

Connector & terminal

H4 non-TURBO without OBD model

(B141) No. 6 — (B135) No. 23:

H4 non-TURBO with OBD model

(B141) No. 6 — (B137) No. 17:

H6 and H4 TURBO models

(B141) No. 6 — (B135) No. 14:

Is the measured value less than the specified
value?

10

Ω

Go to step 6.

Repair open circuit
of harness
between IMM
ECM and ECM.

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 (

−−−−

):

Is the measured value same as the speci-
fied value?

0 V

Go to step 7.

Repair harness
between IMM
ECM and ECM,
because there is
short circuit in bat-
tery voltage line or
ignition switch
“ON” line.

7

CHECK HARNESS OF COMMUNICATION
LINE.
Measure voltage between ECM harness con-
nector terminal and chassis ground.

Connector & terminal

H4 non-TURBO without OBD model

(B135) No. 22, No.23 (+) — Chassis
ground (

−−−−

):

H4 non-TURBO with OBD model

(B137) No. 17, No.18 (+) — Chassis
ground (

−−−−

):

H6 and H4 TURBO models

(B135) No. 5, No.14 (+) — Chassis
ground (

−−−−

):

Is the measured value same as the specified
value?

0 V

Go to step 8.

Repair harness
between IMM
ECM and ECM,
because there is
short circuit in bat-
tery voltage line or
ignition switch
“ON” line.

Step

Value

Yes

No

IM-22

IMMOBILIZER (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH TROUBLE CODE (DTC)

8

CHECK ECM BY INTERFACE CHECK.
1) Connect harness connector to ECM.
2) Disconnect harness connector from IMM

ECM.

3) Perform interface check. <Ref. to IM-7,

INTERFACE CHECK, OPERATION,
Subaru Select Monitor.>
Does “Commun. Line Shorted to Ground”
appear on screen?

“Commun. Line Shorted to
Ground” appears on screen.

Replace ECM.
<Ref. to
FU(H4SO)-45,
Engine Control
Module.> or <Ref.
to FU(H4SOw/
oOBD)-42, Engine
Control Module.>
or <Ref. to
FU(H6DO)-46,
Engine Control
Module.> or <Ref.
to FU(H4DOSTC)-
40, Engine Con-
trol Module.>Then
perform teaching
operation. Refer to
teaching opera-
tion manual (Pub.
No. S0820GZ).

Go to step 9.

9

CHECK ECM BY INTERFACE CHECK.
Perform interface check.
Does “Commun. Line Shorted to Battery”
appear on screen?

“Commun. Line Shorted to Bat-
tery” appears on screen.

Replace ECM.
<Ref. to
FU(H4SO)-45,
Engine Control
Module.> or <Ref.
to FU(H4SOw/
oOBD)-42, Engine
Control Module.>
or <Ref. to
FU(H6DO)-46,
Engine Control
Module.> or <Ref.
to FU(H4DOSTC)-
40, Engine Con-
trol Module.> Then
perform teaching
operation. Refer to
teaching opera-
tion manual (Pub.
No. S0820GZ).

Go to step 10.

10

CHECK ECM BY INTERFACE CHECK.
Perform interface check.
Does “Communication Line not Shorted”
appear on screen?

“Communication Line not
Shorted” appears on screen.

Replace IMM ECM
<Ref. to SL-36,
Immobilizer Con-
trol Module.> and
then replace all
ignition keys
(including the tran-
sponder). Then
perform teaching
operation. Refer to
teaching opera-
tion manual (Pub.
No. S0820GZ).

When “Check
(Time Out)”
appears on
screen, perform
interface check
again.

Step

Value

Yes

No

IM-23

IMMOBILIZER (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH TROUBLE CODE (DTC)

C: DTC P1574 KEY COMMUNICATION FAILURE

DIAGNOSIS:
• Failure of IMM ECM to verify key (transponder) ID code

Step

Value

Yes

No

1

CHECK IMM ECM FUNCTION.
Insert the key to ignition switch (LOCK posi-
tion), measure changes in voltage between
antenna connector terminals.

Connector & terminal

(B142) No. 1 (+) — No. 2 (

−−−−

):

Is the measured value same as the specified
value?

−

30 to 30 V (Approximately 0.1

second after inserting the key.)
0 V (Approximately 1 second
after inserting the key.)

Go to step 2.

Replace IMM ECM
<Ref. to SL-36,
Immobilizer Con-
trol Module.> and
then replace all
ignition keys
(including the tran-
sponder). Then
perform teaching
operation. Refer to
teaching opera-
tion manual (Pub.
No. S0820GZ).

2

CHECK IGNITION KEY (TRANSPONDER).
1) Remove the key from ignition switch.
2) Start engine using other keys that have

undergone the teaching operation, fur-
nished with vehicle.
Does engine start?

Engine starts.

Replace ignition
key (including the
transponder).
Then perform
teaching opera-
tion. Refer to
teaching opera-
tion manual (Pub.
No. S0820GZ).

Replace IMM ECM
<Ref. to SL-36,
Immobilizer Con-
trol Module.> and
then replace all
ignition keys
(including the tran-
sponder). Then
perform teaching
operation. Refer to
teaching opera-
tion manual (Pub.
No. S0820GZ).