2003 HONDA CIVIC Multiplex input

Multiplex Control System
Component Location Index
IGNITION KEY LIGHTTest, page 22'91
lr, J
REAR CEILING LIGHTTest, page 22'96
LIGHT/SPOTLIGHTSTest, page 22-96
GAUGE ASSEMBLY
ECM
MULTIPLEX CONTROL UNIT{Built into the under-dashfus6/relav boxlTroubleshooting, page 22'172Input Test, page 22-175
22-168
t

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.

IMultiplex Control Unit Input Test
Remove the driver's dashboard lower cover (see page 20-59).
Disconnect the under-dash fuse/relay box connectors C, E, F, J, K, O, p, O, X and y.
NOTE: All connectors are wire side of female terminals.
CONNECTOR C {14P}CONNECTOR E I13P)
1.
2.
CONNECTOR F {12P}
GRN/RED {USAIGRN/ORN (Canada)
coNNECTOR P (18P)
CONNECTOR J {8PI
WHT/RED
123
4561
BLK
{cont'd)
GRN/ORN BLU
CONNECTOR K {17P)
I
CONNECTOR O I12P)
CONNECTOR X {8P)CONNECTOR O (8P}
LT GRN/RED GRN/ORN
CONNECTOR Y {13P)
BRN/YEL
BLU/REDBLU/RED
345
67E10 )./12
YELGRN/RED
12457
810/V,/ l,/
WHT/GBN
3567I
,/1,/l,/121517
REDGRN/RED
WHT/BLK
RED/WHT
23,/1,/
618r012
BLK
22-175

Multiplex Control System
Multiplex Control Unit lnput Test (cont'd)
3. Inspect the connector and socket terminals to be sure they are all making good contact
.lftheterminalsarebent,looseorcorroded,repairthemasnecessary,andrecheckthesystem. llthe terminals look OK, go to step 4.
4. Reconnectthe connectorstothe under dash fuserelay box, and make surethese inputtests atthe appropriate connectors on lhe under-
dash fuse/relav box.
. lf any test indicates a problem, {ind and correct the cause, then recheck the system. lf allthe input tests prove OK, the multiplex control unit must be faulty. Replace the under_dash fuse/relay box assembly
CavitvWireTest conditionTest: Desired .esult r Possible cause if resullE qS!q!!e!!ed
J4BLK[J nder all conditionsCheck {or voltage 1o ground:Therc sholl.l he 1V or lessPoor ground (G20'l)An ooen in the wire
Y6BLKlJnder all conditionsCheck for voltage to ground:There should bc 1 V or less.Poor ground 1G501)An ooen in the wire
Y1BFNryELParking brake leverdown, turn theigntion switch ON (ll)
Check for voltage to ground:There should be battery voltagewhile the Brake system indicator ison forthe buld check.
An open in the wireShortto groundFaulty ABS modulatorcontrol unit
Check for voltage to ground:There should be 1V or less when the
J2WHT/REDUnder allconditionsCheck for voltage to groundiThere should be baftery voltage.Blown No.9 (10A)fuse in the under'hoodfuse/relay boxAn oncn in rhc wire
CavitvTest conditionTesi: Oesired resultPossible cause ifresult is notobtained
o3GRNDriver's door openCheck for voltage to ground:There should be 1 V or less-Faulty driver's door switchAn ooen in the wire
Driver's door closedCheck for voltage to ground:There should be 5 V or more.Faulty driver's door switchShort to qround
O4LT GRN/REDPassenger's doorCheck .for voltage 10 ground:There should be 1 V or less.Faulty passenger's door switchAn ooen inthewire
Passenger's doorCheck for voltage to ground:There should be 5 V or more.Faulty passenger's door switchShort to oround
osI]l.l
4.,
F1
F8
GRN/ORN
GRN/ORN
GRN/RED(USA)GRN/ORN(Canada)
Parking brake leverCheck for voltage to groLrnd:There shorl.l be 1 V or less.Faulty parking brake switch. An ooen in thewireCheck for voltage to ground:There should be 5 V or more.
. Faulty parking brake switchShortto ground
o5BLU/REDlgnition switch ON (ll),
driver's seat belt isCheck for voltage to ground:There should be 1V or less.Faulty driver's seat belt switchPoorground (G551)An oDen in the wire
Q6BLU/REDlgnition switch ON (ll)
driver's seat belt isbuckled.
Check {or voltage to ground:There should be 6 V or more.Faulty driver's seat belt switchShortto ground
P18RED
H",=
Check for voltage to ground:There sho0ld be 1V or less-
f -9*:li:'^:**:':s*:*
Faulty hatch latch swrtchPoor ground (G552)An open in the wireFaulty hatch latch switch
X5lgnirion key in the Check for voliage to gtound:ignit on switch Thpre should be I V or lcss
lgnrtron kev our o{ the Check for vollage to ground:
. Faulty ignition key switch. Poor ground (G401). An open in the wire
I : [11y.'::i':::1"' **6
\
22-176

)
Low Fuel lndicatorTest.....................11-158Moonroof Drain Channel SliderReplacement......................................... 20'44
Moonroof FrameRep1acement,,,,,,,,,,.,.,.,.,.,.,.,,,,,,............ 20 42
MoonroolGlassAdiustment ........................................... 20-37Rep1acement......................................... 20 37
Moonroot Limit SwitchAdjustment ........................................-.- 20 46Test ...................................................... 22 113
Moonrool MotorReplacement....-.................................... 2D-41
Oil Pressure SwitchTest ................-.-........-................................ 8-4Replacement.........-................................. 8-16
Oil Pump, EngineOverhau1 ................................................... 8-8
Oil, EngineReplacement...-................-.-...................... 8-5
OPDS UnitReplacement....................................... 23- 124
Outside Mirror HoldersBeplacement......................................... 20-15
Outside Power Mirror ActuatorsTest ...................................................... 22-117Bepf acement..-.................................... 22-1 14
Outside Power Mirror SwitchTest ..-................................................... 22-111
Outsid€ Power MirrorsReplacement............................ ... .. . . . 20-15Component Location lndex .............. 22- 114Circuit Diagram .................................. 22-115Test -..................................................... 22-116
Lower ArmsRemoval/1nsta11ation............................ 18 19
Lubrication SystemComponent Location Index..................... 8-3Test............................................................ 8 4
M
M/TAssemblyRemoval.......... 13-4 Test...................... 22-1 12lnstallation............. 13-8
.........21,35
Disassembly ......................................... 13-14Resassembly .. ... ................. 13-46
M/TChange Leverlnspection ............................................. 13-19Disassembly 8eassemb1y ................... 13-20
M/T Countershaft AssemblyInspection ....................................... 13 31, 33Disassemb1y ......................................... 13-32Resassemb|y ........................................ 13-34
M/T DifferentialComponentLocation Index................. 13-52Adiuslment ........................................... 13-56
M/T Maifthaft Assembly1nspection ... ................................... 13-23, 26Disassembly ......................................... 13 25Resassembly ........................................ 13 28Adjustment ........................................... 13-43
M/T Reverse Shift ForkInspection .................... ........................ l3 19
M/T Shift LevelReplacement......................................... 13-51
Mainshaft BearingsReplacement....,.................................... 13 41
MairtenancelSee section 3)
MILHow to Informatron ............................. 1 1.46
MIL CircuitTroubleshooting .......... .- . . . . ......... 11 97
MirrorsComponentLocation Index................. 20'14
Mode Control MotorReplacement
Moonrool SunshadeRep1acement....................... . . ............. 20 40
Moonroof SwitchTesVRep1acement .............................. 22- l 12
Mooniool Wind Def lectorReplacement.......................-................. 20-38
Moonroof/SunroofComponent Location Index ... 20-35, 22-108Test ........................................................ 20-48Cf rcuit Diagram .................................. 22- 109
MTFInspection/Rep1acement. .......... ........... 13-3
Muhiplex Control SystemComponentLocation lndex ..............22 168Circuit Diagram .................................. 22-1690escription ......................................... 22-17 1Troubleshooting ................................ 22-17 2
Muliiplex Control Unit, Under-dashInput TestEntry Light Control Sysiem ............. 22-92Keyless Entry/Security AlarmSystern .-....................................... 22-155MultiplexControl System .............22 115Wiper/Washer................................. 22'1 41
NoiseTest,,Reduction Condenser
Parking ErakeInspection Adjustment ........... .............. 19-7
Parking Brake CableRep1acement......................................... 19-26
Parking Erake Switch
P
l
Test ...................... 19-10
Test............................... . ...........2135
Moonroof Auto Stop SwitchosTest ...................................................... 22'113
Moon.oot Control Unillnput Test ............................................ 22-110
Moonroof Drein ChannelBeplacement ... . ....... ......................... 20 39
Oil Filte]Replacement............................................. 8-6
Oil Filter Feed PipeReplacement............... . ..-,...,.,,,,,,,,8-7
Oil PanRemoval .............,.,,,,,,,,,,,,.,.,,,.........-....... 7 1 1lnstallation .............................................. 7 -27
Passenger's TraVRemoval/lnstallation ............................ 20-65
PCV ValveBeplacement....................................... 1 1'169Test........................................... l1 169
Piston Rings8ep1acement................................-.-...-.- 7-21
PistonsReplacement...................-....................... 7-181nsta|1ation ...................................... ...1-23
Power R€layTest ...............-.-...................................... 22-51
Power Window Motor, Driver'stesl.....,,,, .,.,,,............
Power Window Motors, Passenger's
Power Window Switch, Masterlnput Test ..........-.........-....................... 22-126Tesr ....... . ............................................ 22 124Replacement....................................... 22-133
N
..............22 101
o
l' ,e
(cont'd)