Subaru Legacy IV (2008 year). Manual - part 1165

IM(diag)-17

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

IMMOBILIZER (DIAGNOSTICS)

B: DTC P1570 ANTENNA

DTC DETECTING CONDITION:
Faulty antenna
WIRING DIAGRAM:

C20

C21

B351

1 2

B281

C:

B351

5 6 7

8

2

1

9

4

3

10

24

22 23

25

11 12 13 14 15

26

27 28

16 17 18 19

20 21

B281

C:

IM-00262

2

1

ANTENNA

BODY INTEGRATED 

UNIT

IM(diag)-18

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

IMMOBILIZER (DIAGNOSTICS)

Step

Check

Yes

No

1

CHECK THE ANTENNA CIRCUIT.
1) Turn the ignition switch to OFF.
2) Disconnect the harness connector from the 
antenna. <Ref. to SL-60, Immobilizer Antenna.>
3) Measure the resistance of antenna circuit.

Connector & terminal

(B351) No. 1 — No. 2:

Is the resistance less than 10 

:? Go to step 2.

Replace the 
antenna. <Ref. to 
SL-60, Immobi-
lizer Antenna.>

2

CHECK ANTENNA CIRCUIT.
1) Disconnect the harness connector from 
body integrated unit.
2) Measure the resistance between harness 
connector and chassis ground.

Connector & terminal

(B281) No. 21 — Chassis ground:

Is the resistance less than 10 

:? Repair the har-

ness.

Go to step 3.

3

CHECK ANTENNA CIRCUIT.
Measure the resistance between harness con-
nector and chassis ground.

Connector & terminal

(B281) No. 20 — Chassis ground:

Is the resistance less than 10 

:? Repair the har-

ness.

Go to step 4.

4

CHECK ANTENNA CIRCUIT.
1) Turn the ignition switch to ON. (engine OFF)
2) Measure the voltage between harness con-
nector and chassis ground.

Connector & terminal

(B281) No. 21 (+) — Chassis ground (–):

Is the voltage 0 V?

Go to step 5.

Repair the har-
ness.

5

CHECK ANTENNA CIRCUIT.
Measure the voltage between harness connec-
tor and chassis ground.

Connector & terminal

(B281) No. 20 (+) — Chassis ground (–):

Is the voltage 0 V?

Go to step 6.

Because the bat-
tery voltage or igni-
tion switch “ON” 
circuit is shorted, 
repair the harness 
between the body 
integrated unit and 
antenna.

6

CHECK BODY INTEGRATED UNIT FUNC-
TION.
1) Turn the ignition switch to OFF.
2) Connect the harness connector to body 
integrated unit.
3) Insert the key into the ignition switch, then 
measure changes in voltage between the 
antenna harness connectors.

Connector & terminal

(B281) No. 20 (+) — No. 21 (–):

Is the voltage –30 — 30 V? 
(Approx. 0.1 second after 
inserting the key) Is the voltage 
0 V? (Approx. 1 second after 
inserting the key)

Go to step 7.

Replace the body 
integrated unit 
<Ref. to SL-56, 
Body Integrated 
Unit.> Replace all 
ignition keys 
(including the tran-
sponder). Execute 
the registration pro-
cedure next. Refer 
to the “PC applica-
tion help for Subaru 
Select Monitor”.

7

CHECK IGNITION KEY (TRANSPONDER).
1) Remove the key from ignition switch.
2) Start the engine using other key which is 
already registered.

Does the engine start?

Replace the igni-
tion key (including 
the transponder). 
Execute the regis-
tration procedure 
next. Refer to the 
“PC application 
help for Subaru 
Select Monitor”.

Replace the body 
integrated unit 
<Ref. to SL-56, 
Body Integrated 
Unit.> Replace all 
ignition keys 
(including the tran-
sponder). Execute 
the registration pro-
cedure next. Refer 
to the “PC applica-
tion help for Subaru 
Select Monitor”.

IM(diag)-19

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

IMMOBILIZER (DIAGNOSTICS)

C: DTC P1571 REFERENCE CODE INCOMPATIBILITY

DTC DETECTING CONDITION:
Reference code incompatibility between body integrated unit and ECM

Step

Check

Yes

No

1

PERFORM REGISTRATION ON IGNITION 
KEY.
Perform registration on all keys of the vehicle. 
Refer to the “PC application help for Subaru 
Select Monitor”.

Is registration for all keys com-
plete?

END

Go to step 2.

2

CHECK FOR ANY OTHER DTC ON DISPLAY. Is any other immobilizer DTC 

displayed?

Check the appro-
priate DTC using 
the “List of Diag-
nostic Trouble 
Code (DTC)”. 
<Ref. to IM(diag)-
14, List of Diagnos-
tic Trouble Code 
(DTC).> Execute 
the registration 
procedure next. 
Refer to the “PC 
application help for 
Subaru Select 
Monitor”.

Replace the ECM. 
<Ref. to 
FU(H4DOTC)-52, 
Engine Control 
Module (ECM).> 
<Ref. to 
FU(H6DO)-38, 
Engine Control 
Module (ECM).> 
Body integrated 
unit <Ref. to SL-56, 
Body Integrated 
Unit.>, and replace 
all the ignition keys 
(including tran-
sponder). Execute 
the registration 
procedure next. 
Refer to the “PC 
application help for 
Subaru Select 
Monitor”.

IM(diag)-20

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

IMMOBILIZER (DIAGNOSTICS)

D: DTC P1572 IMM CIRCUIT FAILURE (EXCEPT ANTENNA CIRCUIT)

DTC DETECTING CONDITION:
Communication failure between body integrated unit and ECM
WIRING DIAGRAM:

MAIN SBF

SBF-8

SBF-3

F/B No.12

A1

B28

B18

C9

C2

B7

C8

B136

C:

C34

C26

E

F/B No.7

M/B No.8

i84

A:

B280

B:

B281

C:

B22

5 6 7

8

2

1

9

4

3

10

24

22 23

25

11 12 13 14 15

26

27 28

16 17 18 19

20 21

B281

i84

1 2

3 4

5 6

7 8

9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

24 25

26 27 28 29

30 31 32 33

34 35

5

4

6 7

8

2

1

9

3

10

22

23

11 12 13 14 15

24 25

26 27

16 17 18

28 29

19 20

21

30

B280

A:

C:

B:

ECM

BATTERY

IGNITION
 SWITCH

B136

C:

1

2

8 9

5

6

3

4

10 11 12

19 20 21

29 30

31

13 14 15 16

17

27

28

18

22 23 24 25 26

7

32 33 34 35

BODY INTEGRATED UNIT

IM-00202