Subaru Impreza 3 / Impreza WRX / Impreza WRX STI. Manual — part 771

IM(diag)-19

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

IMMOBILIZER (DIAGNOSTICS)

Step

Check

Yes

No

1

CHECK BODY INTEGRATED UNIT POWER
SUPPLY CIRCUIT.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from body inte-
grated unit.
3) Measure the voltage between the body inte-
grated unit connector terminal and chassis
ground.

Connector & terminal

(B280) No. 6 (+) — Chassis ground (–):

Is the voltage 10 V or more?

Go to step

2.

Check the harness
for open or short
circuit between
body integrated
unit and fuse.

2

CHECK BODY INTEGRATED UNIT POWER
SUPPLY CIRCUIT.
1) Turn the ignition switch to ON.
2) Measure the voltage between the body inte-
grated unit connector terminal and chassis
ground.

Connector & terminal

(B280) No. 1 (+) — Chassis ground (–):

Is the voltage 10 V or more?

Go to step

3.

Check the harness
for open or short
circuit between the
body integrated
unit and ignition
switch.

3

CHECK BODY INTEGRATED UNIT GROUND
CIRCUIT.
1) Turn the ignition switch to OFF.
2) Measure the resistance between the body
integrated unit connector terminal and chassis
ground.

Connector & terminal

(i84) No. 28 — Chassis ground:
(B280) No. 17 — Chassis ground:
(B281) No. 20 — Chassis ground:
(B279) No. 27 — Chassis ground:

Is the resistance less than 10

Ω?

Go to step

4.

Repair the open
circuit of the body
integrated unit
ground circuit.

4

CHECK GROUND CIRCUIT FOR ECM.
Measure the resistance between the ECM
ground terminal and engine ground.

Is the resistance less than 10

Ω?

Go to step

5.

Repair the ECM
ground circuit.

5

CHECK HARNESS BETWEEN BODY INTE-
GRATED UNIT AND ECM.
1) Disconnect the connector from the ECM
and body integrated unit.
2) Measure the resistance between body inte-
grated unit connector terminal and ECM con-
nector terminal.

Connector & terminal

(B280) No. 4 — (B135) No. 25:
(B280) No. 15 — (B135) No. 24:

Is the resistance less than 10

Ω?

Go to step

6.

Repair the open
circuit of the har-
ness between the
body integrated
unit and ECM.

6

CHECK COMMUNICATION CIRCUIT HAR-
NESS.
1) Turn the ignition switch to ON.
2) Measure the voltage between the body inte-
grated unit connector terminal and chassis
ground.

Connector & terminal

(B280) No. 4 (+) — Chassis ground (–):
(B280) No. 15 (+) — Chassis ground (–):

Is the voltage 6 V or more?

Repair the harness
between body inte-
grated unit and
ECM.

Go to step

7.

7

CHECK COMMUNICATION CIRCUIT HAR-
NESS.
Measure the voltage between ECM connector
terminal and engine ground.

Connector & terminal

(B135) No. 24 (+) — Engine ground (–):
(B135) No. 25 (+) — Engine ground (–):

Is the voltage 6 V or more?

Repair the harness
between body inte-
grated unit and
ECM.

Go to step

8.

IM(diag)-20

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

IMMOBILIZER (DIAGNOSTICS)

NOTE:

Refer to the following inspection when DTC is detected after inspection above. <Ref. to IM(diag)-25, DTC

B1578 METER FAILURE, Diagnostic Procedure with Diagnostic Trouble Code (DTC).>

8

CHECK ECM BY COMMUNICATION SHORT
CHECK.
1) Connect the connector to ECM.
2) Disconnect the connector from body inte-
grated unit.
3) Start the communication short check. <Ref.
to IM(diag)-8, COMMUNICATION LINE
CHECK, OPERATION, Subaru Select Moni-
tor.>

Is the communication short
check OK?

Replace the body
integrated unit.
<Ref. to SL-48,
Body Integrated
Unit.> Register all
ignition keys (tran-
sponders). Refer to
the “REGISTRA-
TION MANUAL
FOR IMMOBI-
LIZER”.

Replace the ECM.
<Ref. to FU(STI)-
59, Engine Control
Module (ECM).>
Perform the regis-
tration procedure
next. Refer to the
“REGISTRATION
MANUAL FOR
IMMOBILIZER”.

Step

Check

Yes

No

IM(diag)-21

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

IMMOBILIZER (DIAGNOSTICS)

D: DTC B1574 KEY COMMUNICATION FAILURE

DTC DETECTING CONDITION:

Communication failure between key and body integrated unit

WIRING DIAGRAM:

Immobilizer system <Ref. to WI-158, WIRING DIAGRAM, Immobilizer System.>

Step

Check

Yes

No

1

CHECK BODY INTEGRATED UNIT FUNC-
TION.
Insert the key into the ignition switch (LOCK
position), then measure changes in voltage
between the antenna connector and the chas-
sis ground.

Connector & terminal

(B415) No. 1 (+) — Chassis ground (–):

Is the maximum voltage more
than 40 V? (Approx. 0.1 second
after inserting the key) Is the
voltage 0 V? (Approx. 1 second
after inserting the key)

Go to step

2.

Replace the body
integrated unit.
<Ref. to SL-48,
Body Integrated
Unit.> Register all
ignition keys (tran-
sponders). Refer to
the “REGISTRA-
TION MANUAL
FOR IMMOBI-
LIZER”.

2

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?

Register ignition
keys (transpon-
ders). Refer to the
“REGISTRATION
MANUAL FOR
IMMOBILIZER”.

Replace the body
integrated unit.
<Ref. to SL-48,
Body Integrated
Unit.> Register all
ignition keys (tran-
sponders). Refer to
the “REGISTRA-
TION MANUAL
FOR IMMOBI-
LIZER”.

B25

B26

B415

1 2

B280

B:

B415

B280

B:

IM-00279

2

1

5

4

6

7 8

2

1

9

3

10

22 23

11 12 13 14 15

24

25 26

16 17

18 19 20

1

2

ANTENNA

BODY INTEGRATED

UNIT

IM(diag)-22

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

IMMOBILIZER (DIAGNOSTICS)

E: DTC B1575 INCORRECT IMMOBILIZER KEY

DTC DETECTING CONDITION:

Incorrect immobilizer key (use of unregistered key in body integrated unit)

Step

Check

Yes

No

1

PERFORM IGNITION KEY REGISTRATION.
Perform registration to all keys used for the vehi-
cle. Refer to the “REGISTRATION MANUAL
FOR IMMOBILIZER”.

Is registration of all keys com-
plete?

End.

Replace ignition
keys (including
transponder)
which cannot be
registered. Go to
step

2.

2

PERFORM IGNITION KEY REGISTRATION.
Perform registration to all keys used for the vehi-
cle. Refer to the “REGISTRATION MANUAL
FOR IMMOBILIZER”.

Is registration of all keys com-
plete?

End.

Replace the body
integrated unit.
<Ref. to SL-48,
Body Integrated
Unit.> Register all
ignition keys (tran-
sponders). Refer to
the “REGISTRA-
TION MANUAL
FOR IMMOBI-
LIZER”.