2003 HONDA CIVIC Wire harness

Fuse/Relay Boxes
Connector to Fuse/Relay Box Index
Under-hood Fuse/Relay Box
lview of tront sidel
- a-------) | | T---r .-:-tt || tL__.1 | I
------tttL""tt tt ttL lL ltl'".-
{View of back side)
SocketRefTerminalConnects to
Ay'C compressor clutch relay
B
Blower motor relay
c
Condenser fan relay
D
E
ELD unit
Headlight relay 1
Headlight relay 2
Horn relay
Radiator fan relay
Rear window defoqqer relay
14
2
15
91'
11
to
5
6
10'l
J
2
4
5
4
4
14
7
3
4
4
4
4
Engine compartment wire harness (see page 22-18)
Engine compartment wire harness (see page 22-18)
Engine compartment wire harness (see page 22-18)
Engine compartment wire harness (see page 22-18)
Engine compartment wire harness (see page 22-18)
Engine compartment wire harness {see page 22-18)
T1 (Batterv)8Starter subharness (see oaqe 22-15)
T101 (Alternator)7Starter subharness {see oaoe 22-'15}
""""-l- tr -l T _l T Il
I tTt Tr,/^-------lFrr^l -/1-l sz- l:!)L' lrt
22-44

Under-dash Fuse/Relay Box
SocketRefTerminal Connects to
B
c
D
E
F
G
H
J
K
M
N
o
P
Power window relay
o
R
S
Starter cut relay
T
Taillight relay
Turn signal/hazard relay
U
W (Memory erase signal (MES)
connector)
X
Y
2
3
1
5
19
9
I
20
24
22
27
26
7
6
10
25
14
18
11
l5
to
17
28
5
6
14
13
12
10
3
:
11'10
1:
.o^
;;
4
8
2
i
nl
al
lt
2
Dashboard wire harness B {see page 22-30)
Dashboard wire harness B {see page 22-30)
Dashboard wire harness B (see page 22-30)
ECM wire harness (see page 22-32)
ECI\4 wire harness (see page 22-32)
Engine compartment wire harness (see page 22-'l8l
Engine compartment wire harness (se e page 22-181
Engine compartment wire harness (see page 22-18)
Engine compartment wire harness (se e page 22-18)
Engine compartment wire harness (see page 22-18)
Dashboard wire harness A (see page 22-26)
Dashboard wire harness A (see page 22-26)
Dashboard wire harness A (see page 22-26)
Dashboard wire harness A (see page 22-26)
Dashboard wire harness A (see page 22-26)
Floor wire harness (see page 22-34)
Floor wire harness (see page 22-34)
ECM wire harness (see page 22-32)
Dashboard wire harness B (see page 22-30)
Multiplex control unit service check connector
Optional connector
Optional connector
Floor wire harness (see page 22-34)
{Plugs directly into the multiplex control(Pluqs directlv into the multiDlex control
unat)
unrl)
I
13
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I] L] L] LI L]
!3 12
22-45

IVehicle Speed Signal Circuit Troubleshooting
Special Tools Required:
Test Harness 07LAJ-PT3020A
Before testing, inspect the No. 4 (10A) and No. 10 (7.5A)
fuses in the under-dash fuse/relay box.
1. Disconnect the 3P connector from the vehicle
speed sensor (VSS) {A).
Connect the test harness only to the engine wire
harness.
Connect the RED test harness clip (B) to the positive
probe of an ohmmeter. Cover the white (C) and
green {D) test harness leads with protective tape (E).
Check for continuity between the RED test harness
clip and body ground,
ls there continuity?
YES Go to step 5.
NO Repair open in the BLK wire between the VSS
and G 101.I
3.
4.
5. Connect the WHT test harness cliD (B) to the
positive probe of a voltmeter, and connect the RED
test harness clip (C) to the negative probe.
Turn the ignition switch ON (ll).
le thara h2ltarv v^ltada?
YES-Go to step 7.
NO Repair open in the BLK,/YEL wire between the
VSS and the under-dash fuse/relay box.l
Disconnect the WHT test harness clip (B).
Connect the GRN test harness clip {D) to the
positive probe of a voltmeter.
Is there 5 V or more?
YES- Go to step 9.
NO Repair short or open in the BLUMHT or WHT/
GRN wire between the VSS and the cruise control
unit, or the ECM.I
(cont'd)
7.
8.
22-65

Gauges
9.
10.
Vehicle Speed Signal Circuit Troubleshooting (cont'dl
Turn the ignition switch OFF.
Connect the other test harness connector (A) to the
VSS (B),
11.Raise the front of the vehicle, and make sure it is
securely supported.
Put the vehicle in neutral with the ignition switch
oN {|| ),
Slowly rotate one wheel with the other wheel
blocked.
Does voltage pulse ttom 0 to about 5 V ot morc?
YES Go to step 14.
NO Replace the VSS.I
't2.
t5.
22-66
14. Disconnect the 22P connector "8" from the gauge
assemDry.
GAUGE ASSEMBLY CONNECTOR B (22P)
Wire side ot female terminals
'15. Connect the positive probe of a voltmeter to the
BLU/WHT wire and the negative probe to ground.
'16. Slowly rotate one wheel with the other wheel
blocked.
Does voltage pulse f rom 0 to about 5 V or more?
YES - Replace the speedometer assembly.I
NO Repair open in the BLUMHTwiTe between
the VSS and the speedometer.l

Power Mirrors
Power Mirror Actuator Replacement
Remove the power mirror (see page 20-15).
Carefully remove the mirror holder from the mirror
housing. Gently pull it out by hand (see page 20-15).
Disconnect the connector.
Remove the cover, then remove the two Torx
screws from the mirror connector.
Record the terminal locations and wire colors.
Cut the wire harness with the wire cutter.
7. Remove the three screws, and separate the mirror
housinq from the mirror base.
'1.
2.
3.
4.
5.
6.
22-118
J
\4
8. Remove the three Torx screws, and separate lhe
actuator (A) from the mirror housing {B).
Route the wire harness {A) ofthe new actuator
through the hole in the bracket (B).9.
\J

Horns
1.
3.
Horn Test/Replacement
Remove the front bumper {see page 20-85).
Disconnect the 1P connector (B), and remove thehorn (A).
Test the horn by connecting battery power to the
terminal (A) and ground to the bracket (B). The horn
should sound.
4. lf it fails to sound, replace it.
22-122
1.
Horn Switch Test
Remove the steering column covers (see page '17-
9).
Disconnecl the dashboard wire harness B 5P
connector (A) from the cable reel (B).
Using a jumper wire . connect the dashboard wire
harness B 5P connector (A) No. 2 terminal to bodyground .
. lf the horns sound, goto step 4.. lf the horns do notsound, checkthese items:- Horn relay- No.7 (15A)fuse in the under-hood fuse/relay
box- Horns (see page 22-122).- An open in the wire
| ../......:....,

I
4. Reconnect the dashboard wire harness B 5P
connector {A), and disconnect the horn switch
positive 1P connector (B).
Using a jumperwire, connectthe horn switch
positive 1P connector (B) to ground
. lf the horns sound, go to step 6.. lf the horns do notsound, replacethecable reel.
Reconnect the horn switch positive 1P conector (B).6,
22-123
1.Using a jumper wire, connent the steering wheel to
body ground.
Close the contacts between the horn plate and the
contact plate.
. lf the horns sound, replacethe steering column.. lf the hornsdo notsound, replacethe horn and
contact plate.
8.

ISystem Descriptions
The Multiplex Control System has four internal
functions:. Multiplexing (send multiple signals over sharedwtres). Wake up/sleep (runs at full power only on demand toreduce battery draw). Fail-safe (fixes or ignores faulty signals). Self-diagnosis (Mode 1 for the system, Mode 2 for
input lines)
The system controls the function of these circuits:. Entry lightcontrol (ignition key lightandceiting light). Wiper/washer intermittent wipe and park functions. Keyless/power door lock. Meter assembly, temperature gauge, and indicator
lights. HVAC (compressor and fan control). Key-in reminder. Headlight reminder. Seatbelt reminder
JI
/ar
22-171
Multiplex Communication
To reduce the number of wire harnesses, digital signals
are sent via shared multiplex communication linesrather than sending normal electrical signals throughindividual wires.. The input signals from each switch are converted todigital signals at the central processing unit (CpU).. The digital signalsaresentfromthetransmitting unitto the receiving unit as serial signals.. The transmitted signal is converted to a switch signalat the receiving unit, and it operates the related
component or monitors a swltch.. There are exclusive communicalion lines between
the ECM, the gauge assembly, and the under,dash
fuse/relay box.
Wake-up and Sleep
The multiplex control system has "wake-up" and"sleep" functions to decrease parasitic draw on the
battery when the ignition switch is OFF.. ln the sleep mode, the multiplex control unit stops
functioning (communication and CPU control) when it
is not necessary for the system to operate.. As soon as any operation is requested (for example, adoor is unlocked), the related control unit in the sleep
mode immediately wakes up and begins to function.. When the ignition switch is turned OFF, and the
driver's or front passenger's door is opened, then
closed, there is about a 10 second delay before the
control unit goes from the wake-up mode to the sleepmode.. lf any door is open, the sleep mode will not function.. lf a key is in the ignition switch, the sleep mode will
not function.. When in sleep mode, the draw is reduced from
70 80 mA to less than 10 mA.
Fail-safe
To prevent improper operation, the multiplex controlsystem has a fail-safe function. In the fail-safe mode,
the output signal js fixed when any part of the systemmalfunctions (for example a faulty control unit orcommunication line).
Each control unit has a hardware fail-safe function thatfixes the output signal when there is any CPUmalfunction, and a software fail-safe function thatignores the signal from the malfunctioning control unitand allows the system to operate normally.