2003 HONDA CIVIC multiplex control unit under dash

ABS Components
q,
CONNECTOR A {12P)BRAKE PEDAL POSITIONSWITCH 4P CONNECTOR
Circuit Diagram (cont'd)
UNDER-HOOD FUSE/RELAY BOX CONNECTORSCONNECTOR A {12P) CONNECTOR B {2P}
UNDER.DASH FUSE/RELAY BOX CONNECTORSCONNECTOR I {5P)CONNECTOR K I17P)MULTIPLEX CONTROLUNIT 13P CONNECTOR
CONNECTOR B I22PI
1l2l3l,/15
GAUGE ASSEMBLY CONNECTORS
CONNECTOR A I22P)
WHEEL SENSOR 2P CONNECTORS
FRONT
J --T:-l Ltqtt/)l'l L_.:-:J r\-r-----Tr'e:l
RIGHT.REAR LEFT-REAR
tslTt?t /J 1T-1\I tL | rlziJ
Terminal side of male lerminals
ABS CONTROL UNIT 3IP CONNECTOR
OATA LINK CONNECTOR {16P)
Terminal side of female terminals
Wire side of female terminals
1234567
810111213141511
123,/ ,/
67891011n213
1245678I11121415
161118192021/1,/1,/vl,/l
/t,/t/t,/t/
19-44

8. Connect the No.4 terminal ofheatercontrol
connector A (14P) to body ground with a jumper
wire,
HEATER CONTROL PANEL CONNECTOR A I14P}
BLU
23456
78Ir0lx1112l3t4
JUMPER WIBE
Wire side of female terminals
Does the A/C system come on?
YES Replace the heater control panel.!
NO Refer to the multiplex control system (see
page 22-168).1
Using the Backprobe Set, connect the No. 9
terminal of under-dash fuse/relay box connector
F (12P) to body ground with a jumper wire.
UNOER.DASH FUSE/RELAY BOX CONNECTOR F {12P}
9.
25
61B g lrotll2
BLU/WHT
JUMPERWIRE
Wire side of female terminals
Does the NC system come on?
YES Go to step 10.
NO- Refer to the multiplex control system (see
page 22-168).1
NOTE: Check for multiplex codes in mode '1. Follow
the troubleshooting {or any codes found. lf no
codes are found, subsititute a known-9ood
multiplex control unit and a ECM one at a time.
Disconnect the Ay'C pressure switch 2P connector
and under-dash fuse/relay box connector F { 12P).
10.
'13.
21-33
11. Check for continuity between the No. 2 terminal of
the A,/C pressure switch 2P connector and the No. 9
terminal of under-dash fuse relav box connector
F t12Pt.
A/C PRESSURE SWITCH 2PCONNECTORWire side of female terminals
UNDER.OASH FUSE/RELAY BOX CONNECTOR F (12P)
Wire side of fenale lerrrinal'
ls there continuity?
YES Go to step 12.
NO Repair open in the wire between the
under-dash fuse/relay box and the A,,/C pressure
switch.I
Check for continuity between the No. 1 and No. 2
terminals of the A,/C pressure switch.
12.
A/C PRESSURE SWITCH
ls there continuity?
YES Repair open in the wire between the heater
control panel and the A,/C pressure switch.l
NO Go to step 13.
check for proper Ay'C system pressure.
ls the pressure within specitications?
YES Replace the AilC pressure switch.l
NO Repair the AilC pressure problem.I

Relay and Gontrol Unit Locations
Dashboard
_DAYTIME RUNNING LIGHTS EELAY lCanada)lWire colorsr RED, RED/YEL, ILRED/BLK and RED/8LU I_LOW BEAM CUT RELAY lcanada) _lWire colors: REDMHT, RED/BLK, ILBEDA/EL and RED/BLU I
KEYLESS RECEIVER UNIT
CRUISE CONTROL UNIT
'
'-.:- ':
..? ;,
POWER WINOOW RELAY
TURN SIGNAL/HAZARD RELAY
TAILLIGHT RELAYUNDER.DASHFUSE/RELAY BOX; .[:_- -
-l:r --
22-8
MULTIPLEX CONTROL UNIT

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
tn--rlI U LI L.] L.Jh--n-UL]L]UL]
I] L] L] LI L]
!3 12
22-45

Power Distribution
Fuse to Components lndex
Under-hood Fuse/Relay Box
Fuse
Number
AmpsWire ColorComponent(sl or Circuit(s) Protected
'I204BLUI/ELCondenser fan motor
BLU/REDAy'C compressor clutch
15AWHT/GRNDash lights, Front parking lights, Front side marker lights, License plate
liqht, Rear side marker liqhts, Tailliqhts
7.5AWHT/BLUCarqo area liqht, Ceilinq liqhts. lqnition Kev liqht. Sootliohts
204BLU/BLKRadiator fan motor
510AWHT/BLKTurn siqnal/hazard relav, Turn siqnal liqhts
15AWHT/BLKCKP sensor, ECM, IAC valve, lmmobilizer control unit-receiver, Injectors,
PGM-FI main relav 1 and 2. TDC sensor
715AWHT/GRNBrake lights, Brake signals (to ABS modulator-control unit, Cruise control
unit, ECM)
BLU/REDi1 Orns
820AWHT/GRNABS modulatorcontrol unit
910AWHT/REDAudio unit, Data link connector (DLC), Gauge assembly, lmmobilizer
control unit-receiver, lmmobilizer indicator light. Keyless receiver unil,
lvlultiDlex control unit
1040AWHT/REDABS modulator-control unit
1130AB LK/YE LNoise condenser, Rear window defoqqer
40ABLU^^/HTBlower motor
IJ40AWHT/BLKNo. 7 fuse (in the under-dash fuse/relav box), Power window relav
1440AWHT/REDNo.2 and No.3 fuses (in the under-dash fuse/relav box)
t515AREDI/ELDaytime running lights control unit (Canada), Daytime running lights relay
{Canada), Hioh beam indicator liqht. Left headliqht
16204WHTMultiplex control unit
1715AREDDavtime runninq liqhts control unit (Canada). Rioht headlioht
1860AWHTiBLUEPS control unit
1980ABatterv. Power distribution
2040A'
50A'?
WHTlgnition switch (BAT)
* 1: USA" 2. Canada
O: Spare fuse
t t"| lll Itt 4t I
l l---- E'l E,l E,l r--r r---r t__J i; i6'!/'
E,l E,l E,l Eol E l f__--lI l'lr]n | |I r L__J,a ,..r^{-------l^-,
n[:]$"Lrt " N2, nf - r^l
22-46

Under-dash Fuse/Relay Box
Fuse
Number
AmpsWire ColorComponent(s) or Circuit(s) Protected
115ABLKA/VHTlgnition coils
2204WHT/REDAirlfuel ratio sensor, ECM
310ARED/BLUDaytime running Iights control unit {Canada)10ABLI(ORNAir/fuel ratio sensor relay, Alternator, CMP sensor, Cruise control main
switch, Cruise control unit. ELD unit, Evaporative emission (EVAP) bypass
solenoid valve, Evaporative emission (EVAP)canister purge valve,
Evaporative emission (EVAP) canister vent shut valve, Secondary H02S,
Vehicle speed sensor
5Not used
67.5AYEUGRNMoonroof control unit, Moonroof open and close relay, Power window
relaV
7204GRNMoonroof motor
I7.5AYEUREDAudio unit
910AGRNOPDS unit, Rear window wiper motor, Rear window washer motor, Rear
window wiper intermittent control unit
107.54YELBack-up lights, Cruise indicator light, EPS control unit, Gauge assembly,
Keyless receiver unit, Multiplex control unit, Security control unit
connector (optional)
117.5ABLIVORNABS modulator-control unit
127.5AYEUREDDaytime runnino liohts control unit (Canada)
1310APNKSRS unit't410ABLK/YE LA,,/C compressor clutch relay, Blower motor relay, Condenser fan relay,
Heater control panel, Power mirror actuator, Power mirror defogger(Canada), Radiator fan relay, Rear window defogger relay, Recirculation
control motor1ENot used
loNot used
1715AYE L/B LKECM, Fuel pump
B LK/YE L>H> Unrr
1815AYEUGRNAccessory power socket
197.5AYEUBLKTurn siqnal/hazard relav, Turn siqnal liohts
2030AGRN/BLKMultiplex control unit, Windshield washer motor. Windshield wioer motor21Not used
22204GRN/BLKPassenqer's window motor
2320A.G R N,A/VHTDriver's window motor
24Not used
25Not used
__^:Hr tl_l
f at-t
at I
r^,rl fl
!!;r -
!339,i;s!!sf Fnf : |rnITf
22-47

Gauges
2.
3.
Gauge Assembly Replacement
1.Remove the instrument panel (see page 20-59),
then remove the upper column cover {see page 17-
Place a clean shop towel (A) under the gauge
assembly to prevent scratching the steering
colum n or dash panel.
Remove the screws from the gauge assembly (B).
Disconnect the connectors (C), and remove thegauge assemDry.
Installthe gauge assembly in the reverse order of
removal.
Coolant Temperature Gauge
Troubleshooting
Before testing, check the No. I { 10A) fuse in the under-
hood fuse/relay box and the No. '10 (7.5A) fuse in the
under dash fuse/relay box.
1. Start the engine, and check the malfunction
indicator lamp (MlL).
Does the MIL come on?
YES- Troubleshoot the cause of the ECM DTC (see
page 1 1-57), and recheck.
NO-Go to step 2.
2. Check for a multiplex control unit DTC (see page
22,168).
ls a DTC ind icated?
YES Troubleshooting the cause of the multiplex
control unit DTC {see page 22-168), and recheck.
NO Go to step 3.
3. Do the communication line check with the self-
diagnosis procedure (see page 22-56).
ls the word "Error" indicated on the odo/ttip
d isplay ?
YES The gauge cannot receive the signal from the
multiplex control unit and the ECI\,4. Check for an
open in the WHT/GRN wire (gauge connector
terminal B 13). lf no open is found, go to step 5.
NO Go to step 4.
4. Do the gauge drive circuit check with the self-
diagnosis procedure (see page 22-56).
Does the temperature gauge needle sweep lrom
the minimum position to the maximum, then tetutn
to the minimum position?
YES Go to step 5.
NO Replace the gauge assembly.l
5. Substitute a known-good ECM and recheck.
Did the symptom/ ind ication go away?
YES Replace the ECM.
NO Substitute a known good gauge assembly. lf
the symptom/indication goes away, replace thegauge assembly.l
4.
22-64

I
5. With the connectors stilldisconnected, make these input tests at the connector'
. lf anv test indicates a problem, find and correct the cause, then recheck the system. lf all the inpul tests prove OK, go to step 6.
6.Reconnect the connectors to the under dash fuse/relaV box, and make these input tests at the appropriate connectors on the under-dash
fuse/relay box.
.lfanytestindicatesaproblem,findandcorrectthecause,thenrecheckthesystem..lfalltheinputtestsproveOK,themultiplexcontrolunitmustbefaulty.Replacetheunder'dashfuse/relaYboxassemblY
CavitvWireTest conditionTest: Desired resultPossible cquse il result is not obtained
K28LU/ORNlJnder allconditionsCheck for continuity between the K2terminal and the keyless receiverunit 5P connector No. 2 terminal:There should be continuitv.
An open in the wire
o7GRN/REDCejling light switch inmiddle position.Attach to ground:Ceiling light(s)should come on.Blown No. 3 (7.5A) fuse in the under hood
Blown bulbFaulty ceiling lightAn ooen in the wire
X8WHT/BLKUnder allconditionsAttach to ground:lgnition key light should come on.Elown No.3 (7.5A)fuse in the under hoodfuse/relay boxFaulty ignition key light (LED)
An ooen in the wire
CavitvWireTest conditionTest: Desired resultPosq!!!c sq!!ej1!.9!!!!j €d
P18REDHatch openCheck for voltage to ground:There should be 1 V or less.Poor ground (G552)
Fauhy hatch latch switchAn open inthewire
Hatch closedCheck for voltage to ground:There should be 5 v or more.Faulty hatch latch switchShortto oround
Q3GRNDriver's door openCheck for voltage to ground:There should be 1 V or less.Faulty drlver's door switchAn oDen in the wire
Driver's door closedCheck for voltage to ground:Thar. shoul.l he 5 V or more.Faulty driver's door switch
o4LT GRN/BED
RED^vHT
Passenger's doorCheck for voltage to ground:There should be 1 V or less.
' Faulty passenger's door switch' An onen inthewire
Passenger's doorcroseoCheckfor voltage to ground:There should be 5 Vor more.
. Faulty passenger's door switch. Shor o oround
X5lgnition key insertedinto the ignitionCheck for voltage to ground:There should be 1 V or less.Poor ground (G401)
Faulty ignition key switchAn ooen in the wire
lgnition key removedfrom the ignitionCheck for voltage to ground:There should be 5 V or more.Faulty ignition key switchShort to ground
Y8YEUREDDriver's door lockknob switch lockedCheck for voltage to ground:There should be 1 V or less.Poor ground {G501)Faulty driver's door lock knob switchAn ooen in the wire
Driver's door lockkn6h cwirch Inl6cke.lCheck for voltage to ground:There should be 5 V or more.Faulty driver's door lock knob switchShort to oround
22-93