Subaru Impreza 3 / Impreza WRX / Impreza WRX STI. Manual - part 793

WIRING SYSTEM

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Page

1.

Basic Diagnostic Procedure  .......................................................................3

2.

Working Precautions  ................................................................................14

3.

Power Supply Circuit ................................................................................15

4.

Ground Circuit  ..........................................................................................23

5.

Engine Electrical System  .........................................................................32

6.

Radiator Fan System  ...............................................................................64

7.

Charging System ......................................................................................65

8.

Starter System  .........................................................................................66

9.

Vehicle Dynamics Control System  ...........................................................67

10.

Tire Pressure Monitoring System .............................................................71

11.

Driver’s Control Center Differential Control System .................................72

12.

Air Conditioning System ...........................................................................74

13.

Airbag System ..........................................................................................82

14.

Seat Belt Warning System  .......................................................................86

15.

Occupant Detection System .....................................................................87

16.

Seat Heater System  .................................................................................88

17.

Headlight System  .....................................................................................90

18.

Headlight Beam Leveler System ..............................................................93

19.

Front Fog Light System ............................................................................94

20.

Back-up Light System  ..............................................................................95

21.

Stop Light System  ....................................................................................96

22.

Clearance Light and Illumination Light System  ........................................98

23.

Turn Signal Light and Hazard Light System ...........................................103

24.

Interior Light System  ..............................................................................106

25.

Front Wiper and Washer System  ...........................................................109

26.

Rear Wiper and Washer System ............................................................110

27.

Wiper Deicer System  .............................................................................112

28.

Audio System  .........................................................................................113

29.

Front Accessory Power Supply Socket System  .....................................121

30.

Rear Accessory Power Supply Socket System ......................................122

31.

Navigation System  .................................................................................123

32.

Horn System  ..........................................................................................129

33.

Power Window System  ..........................................................................130

34.

Remote Control Mirror System ...............................................................134

35.

Rear Defogger System ...........................................................................135

36.

Combination Meter System ....................................................................136

37.

Speedometer System .............................................................................146

38.

Clock System  .........................................................................................147

39.

Fuel Gauge System  ...............................................................................148

40.

Coolant Temperature System  ................................................................149

41.

Oil Pressure Warning Light System  .......................................................150

42.

Parking Brake / Brake Fluid Level Warning Light System ......................151

43.

Rear Differential Oil Temperature Warning Light System  ......................152

44.

Sunroof Control System  .........................................................................153

45.

Security System  .....................................................................................154

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WIRING SYSTEM

46.

Immobilizer System ................................................................................158

47.

Keyless Entry System  ............................................................................159

48.

Cruise Control System  ...........................................................................163

49.

CAN Communication System .................................................................171

50.

Rearview Mirror System .........................................................................173

51.

Harness Components Location ..............................................................174

52.

Front Wiring Harness  .............................................................................176

53.

Bulkhead Wiring Harness (In Engine Compartment)  .............................178

54.

Bulkhead Wiring Harness (In Compartment)  .........................................180

55.

Engine Wiring Harness and Transmission Cord  ....................................183

56.

Instrument Panel Wiring Harness  ..........................................................187

57.

Rear Wiring Harness ..............................................................................189

58.

Door Cord ...............................................................................................192

59.

Rear Wiring Harness and Trunk Lid Cord  ..............................................194

60.

Rear Wiring Harness and Rear Gate Cord  ............................................196

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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 SYMP-

TOM

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) Touch connector (B) with the positive probe. The

voltmeter 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

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Basic Diagnostic Procedure

WIRING SYSTEM

3. HOW TO DETERMINE AN OPEN CIR-

CUIT

1) WITH VOLTMETER:

An  open  circuit  is  determined  by  measuring  the

voltage between respective connectors and ground

using a voltmeter, starting with the connector clos-

est to the power supply. The power supply must be

turned ON so that current flows in the circuit. If volt-

age is not present between a particular connector

and ground, the circuit between that connector and

the previous connector is open.

2) WITH OHMMETER:

Disconnect all connectors affected, and check con-

tinuity in the wiring between adjacent connectors.

When the ohmmeter indicates “infinite”, the wiring

is open.

4. HOW TO DETERMINE A SHORT CIR-

CUIT

1) WITH TEST LIGHT:

Connect  a  test  light  (rated  at  approx.  3  watts)  in

place of the blown fuse and allow current to flow

through the circuit. Disconnect one connector at a

time from the circuit. Starting with the one located

farthest from the power supply. If the test light goes

out when a connector is disconnected, the wiring

between  that  connector  and  the  next  connector

(farther from the power supply) is shorted.

2) WITH OHMMETER:

Disconnect all affected connectors, and check con-

tinuity between each connector and ground. When

the ohmmeter indicates continuity between a par-

ticular  connector  and  a  ground,  that  connector  is

shorted.

Open circuit or wiring

12V

V

V

0V

WI-02742

Open circuit

WI-09860

Shorted wiring

Test light

Fuse holder

WI-02744

Shorted connector

WI-02745