Subaru Legacy IV (2008 year). Service manual - part 1187

LAN(diag)-82

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

LAN SYSTEM (DIAGNOSTICS)

Step

Check

Yes

No

1

CHECK DTC.
Connect the Subaru Select Monitor and read 
the DTC of the body integrated unit.

Are there DTCs other than 
B1500?

Perform diagnosis 
according to other 
DTC.

Go to step 2.

2

CHECK DTC.
Check the DTC displayed in the body integrated 
unit.

Is the DTC displayed a current 
malfunction?

Check the connec-
tion of harness 
connectors. Go to 
step 3.

Go to step 4.

3

CHECK DTC.
Turn the ignition switch to OFF and read DTCs 
again.

Is B1500 current malfunction?

Go to step 4.

Go to step 7.

4

CHECK HARNESS.
1) Disconnect the body integrated unit connec-
tor (i84) and keyless entry control module con-
nector (i96).
2) Measure the resistance between har-
nesses.

Connector & terminal

(i84) No. 9 — (i96) No. 3:

Is the resistance less than 10 

:? Go to step 5.

Repair the open 
circuit of harness 
or replace har-
ness.

5

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

Connector & terminal

(i84) No. 9 — Chassis ground:

Is the resistance less than 1 M

:? Repair the short 

circuit of harness 
or replace har-
ness.

Go to step 6.

6

CHECK HARNESS.
1) Turn the ignition switch to ON.
2) Measure the voltage between harness con-
nector and chassis ground.

Connector & terminal

(i84) No. 9 (+) — Chassis ground (–):

Is the voltage 6 V or more?

Repair the short 
circuit of harness 
or replace har-
ness.

Go to step 7.

7

CHECK OPERATION.
Check the door lock operation when the doors 
LOCK/UNLOCK using manual LOCK switch.

Does it operate on switch oper-
ation?

Go to step 8.

Replace the body 
integrated unit. 
<Ref. to SL-56, 
REMOVAL, Body 
Integrated Unit.>

8

CHECK OPERATION.
1) Remove the ignition key.
2) Close all the doors, and then perform the 
LOCK/UNLOCK operation on keyless entry 
operation.

Does it operate?

Temporary poor 
contact occurs.

Replace the key-
less entry control 
module. <Ref. to 
SL-54, REMOVAL, 
Keyless Entry Con-
trol Module.>

LAN(diag)-83

General Diagnostic Table

LAN SYSTEM (DIAGNOSTICS)

13.General Diagnostic Table

A: INSPECTION

Read the DTC or inspect and diagnose the following data in the current data display using Subaru Select
Monitor.

1. LAN SYSTEM

Item

Operation

Specifications

Note

YES

NO

DTC

DTC is not displayed when inspect-
ing all DTCs.

DTC is not 

displayed.

Perform the diag-
nosis according to 
DTC.

 — 

Coolant Temp.

Check the current data display of 
ECM, TCM and body integrated 
unit. Three data value are the 
same.

Same values

Inspect LAN 
system.

If engine coolant tempera-
ture sensor is not OK, 
inspect the sensor circuit.

Rr Defogger SW

It turns to ON when pressing 
switch. (Low-speed CAN is OK)

Turns to ON.

Inspect rear 
defogger switch.

Rear defogger switch is 
connected with Low-
speed CAN.

Rr defogger output

When switch input, it is output.

Output

Check the body 
integrated unit.

If not operating with out-
put, check the rear defog-
ger relay.

Door lock SW

When locked with door lock switch, 
it turns to ON.

Turns to ON.

Inspect door lock 
switch.

The door lock switch is 
connected to the Low-
speed CAN.

Door lock actuator

When locked with door lock switch, 
it is output.

Output

Check the body 
integrated unit.

 — 

LAN(diag)-84

General Diagnostic Table

LAN SYSTEM (DIAGNOSTICS)

2. BODY INTEGRATED UNIT

Item

Operation

Specifications

Note

YES

NO

Illumination VR 
power supply

Operate the illumination volume, 
illumination light is controlled 
according to the change of voltage 
on data display.

Illumination light is 

controlled with 

changing of data.

Inspect the illumi-
nation volume.

 — 

Fuel level resis-
tance

Check the fuel level resistance and 
fuel level resistance 2. Both resis-
tances are same.

Same values

Inspect the body 
integrated unit.

Compare the input and 
output values of body inte-
grated unit.

R wiper ON/INT 
SW input

When rear wiper SW to ON, data 
display turns to ON.

Turns to ON.

Inspect the rear 
wiper switch.

 — 

R wiper output

When rear wiper switch to ON, out-
put signal turns to ON.

Turns to ON.

Check the body 
integrated unit.

If not operate with output 
turned to ON, check the 
rear wiper motor.

Keyless Entry

Keyless entry LOCK/UNLOCK the 
doors.

Operate

Inspect the key-
less antenna.

If the antenna is OK, 
replace the body inte-
grated unit.

Brake Switch

When brake pedal is depressed, it 
turns to ON.

Turns to ON.

Inspect the brake 
switch.

 — 

Shift Lock Solenoid

The shift lock releases when 
depressing the brake pedal.

Released

Inspect the shift 
lock.

 — 

Body integrated 
unit registration 
function setting

Does Vehicle equipment corre-
spond to setting values?

Correspondence

Reconfigure the 
values according to 
vehicle equipment.

 — 

Customizing

When changing customize setting, 
the registration completes correctly.

Registered

Inspect the body 
integrated unit.

 — 

Manual Mode

Switch the shift (UP/DOWN) on 
Manual mode. Indicator is changed 
in 1 — 2.

Change

Inspect the shift 
lever.

 — 

Function check

Each checking item operate cor-
rectly. (Except for not equipped)

Operate

Inspect for non-
functional actuator.

 — 

Security

After locking with keyless entry sys-
tem and open the door, the security 
system operates and the horn 
sounds.

Horn sounds. 

(Security system 

operates.)

Inspect the secu-
rity system.

 — 

WI-3

Basic Diagnostic Procedure

WIRING SYSTEM

1. Basic Diagnostic Procedure

A: BASIC PROCEDURES

1. GENERAL DESCRIPTION

The most important purpose of diagnostics is to
quickly determine which part is malfunctioning, to
save time and labor.

2. IDENTIFICATION OF TROUBLE SYMPTOM

Determine what the problem is based on the symp-
tom.

3. PROBABLE CAUSE OF TROUBLE

Look at the wiring diagram and check the system’s
circuit. Then check the switch, relay, fuse, ground,
etc.

4. LOCATION AND REPAIR OF TROUBLE

1) Using the diagnostics, narrow down the causes.
2) If necessary, use a voltmeter, ohmmeter, etc.
3) Before replacing certain component parts
(switch, relay, etc.), check the power supply,
ground, for open wiring harness, poor connectors,
etc. If no problem is encountered, check the com-
ponent parts.

5. SYSTEM OPERATION CHECK

After repairing, ensure that the system operates
properly.

B: BASIC INSPECTION

1. VOLTAGE MEASUREMENT

1) Using a voltmeter, connect the negative lead to a
good ground point or negative battery terminal and
the positive lead to the connector or component ter-
minal.
2) Contact the positive lead of the voltmeter on
connector (A). The voltmeter will indicate a voltage.
3) Shift the positive lead to connector (B). The volt-
meter will indicate no voltage.

4) With the test set-up held as it is, turn the switch
to ON. The voltmeter will indicate a voltage and, at
the same time, the light will illuminate.

5) The circuit is in good order. If a problem such as
a light failing to illuminate occurs, use the proce-
dures outlined above to track down the malfunc-
tion.

2. CIRCUIT CONTINUITY CHECKS

1) Disconnect the battery terminal or connector so
there is no voltage between the check points.
Contact the two leads of an ohmmeter to each of
the check points.
If the circuit has diodes, reverse the two leads and
check again.
2) Use an ohmmeter to check for diode continuity.
When contacting the negative lead to the diode
positive side and the positive lead to the negative
side, there should be continuity.
When contacting the two leads in reverse, there
should be no continuity.

3) The symbol “

 — 

” indicates that continuity

exists between two points or terminals. For exam-
ple, when a switch position is at “3”, continuity ex-
ists among terminals 1, 3 and 6, as shown in the
table below.

To power

Fuse

supply

Switch

Light

V

(A)

(B)

WI-02739

Continuity  

No continuity

WI-02740

Terminal

Switch  Position

OFF

1

2

3

4

1

2

3

4

5

6

WI-02741