2003 HONDA CIVIC key

Transmitter Test
NOTE:. lf the doors unlockorlockwiththetransmitter, but
the LED on the transmitter does not come on, the LED
is faulty. Replace the transmitter,. lf anydoor isopen, you cannotlockthedoorwiththe
transmrtter.. lf you unlocked the doors with the transmitter, but do
not open any of the doors within 30 seconds, the
doors relock automatically.. The doors do not lock or unlock with the transmitter if
the ignition key is inserted in the ignition switch.
1. Press the lock or unlock button five or six times to
reset the transmitter.
. lf the locks work, the transmitter is OK.. lf the locks don't work, go to step 2.
2. Open the transmitter and check for water damage.
. lf you find any water damage, replace the
transmrtter.. lf there is no waterdamage, go to step 3.
3. Replace the transmitter battery (A) with a new one,
and try to lock and unlock the doors with the
transmitter by pressing the lock or unlock button
five or six times.
. lf the doors lock and unlock, the transmifter is OK.. lf the doors don't lock and unlock, go to step 4.
Reprogram the transmitter, then try to lock and
unlock the doors.
. lf thedoors lockand unlock.thetransmitter is OK.. lf the doors don'tlockand unlock, replacethe
transmitter.
4.
Transmitter Programming
Storing transmitter codes:
The codes of up to three transmitters can be stored in
the keyless receiver unit memory. (lf a fourth code is
stored. the code which was input first will be erased.)
NOTE: lt is important to maintain the time limits
between the steps. Make sure the doors and the hatch
are closed.
1. Turn the ignition switch ON (lli.
2. Within 1 to 4 sec., push the transmitter lock or
unlock button with the transmitter aimed at the
receiver in the multiplex control unit behind the
driver's side of the dash.
3. Within 1 to 4 sec., turn the ignition switch OFF.
4. Within 1 to 4 sec., turn the ignition switch ON (ll).
5. Within 'l to 4 sec., push the transmitter lock or
unlock button with the transmitter aimed at the
receiver in the multiplex control unit behind the
driver's side of the dash.
6. Within 1 to 4 sec., turn the ignition switch OFF.
7. Within 4 sec., turn the ignition switch ON (ll).
8. Within 1 to 4 sec., push the transmitter lock or
unlock button with the transmifter aimed at the
receiver in the mupltiplex control unit behind the
driver's side of the dash.
9. Within 1 to 4 sec., turn the ignition switch OFF,
'10. Within 4 sec., turn the ignition switch ON (ll).
11. Within 1 to 4 sec., push the transmitter lock or
unlock button with the transmitter aimed at the
receiver in the multiplex control unit behind the
driver's side of the dash.
12. Confirm you can hearthe sound ofthe door lock
actuators. Within 1 to 4 sec., push the transmitter
lock or unlock button again,
13, Within 10 sec., aim the transmitters (up to two
additional ones) whose codes you want to store at
the receiver, and press the transmitter lock or
unlock buttons.
Confirm that you can hear the sound of the door
lock actuators after each transmitter code is stored.
14. Turn the ignition switch OFF, and pull out the key.
'15. Confirm proper operation ofthe transmitter.
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lmmobilizer System
Component Location Index
INOICATOR LIGHTBulb Replacement, page 22 63ECMReplacement, page 11-4Substitute known-good for testing,page 11-5
IMMOBILIZER CONTROL UNIT.RECEIVERTroubleshooting, page 22-165Replacement, page 22-167
TRANSPONDER(8uilt into the ignition key)
22-162

System Description
The vehicle is equipped with an immobilizer system that will disable the vehicle unless the proper ignition key is used.This system consists of a transponder located in the ignition key, an immobilizer control unit-receiver, an indicatorlight, and the ECM.
When the key is inserted in the ignition switch and turned to the ON {ll) position, the immobilizer control unit-receiversends power to the transponder in the ignition key. The transponder then sends a coded signal back to the immobilizer
control unit-receiver which then sends a coded signal to the ECI\4.
iEl'JUiliii'tlun"oona"|.r KEYCYLTNDER
lf the proper key has been used, the immobilizer indicator light will come on for about 2 seconds, then go off.lf the wrong key has been used or the code was not received or recognized by the unit, the indicator light will comeon for about 2 seconds, then it will blink until the ignition switch is turned OFF.lf the ignition switch is turned OFF, the indicator will blink for about 5 seconds to signal that the unit has reset
correctly, then the indicator will go off.
lf the customer has lost his key, and cannot start the engine, contact Honda Customer Relations.
IMMOBILIZER INDICATOR LIGHT BLINKING PATTERN:
IGNITION SWITCHON
OFF
PROPER KEYINSERTEDINDICATORLIGHTON
WRONG KEYINSERTEDINDICATORLIGHTON
OFF
(| i.,
IMMOBILIZER CONTROL UNIT.RECEIVER
)
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)
I
Troubleshooting
Before troubleshooting the immobilizer system,
troubleshoot any EClvl Diagnostic Trouble Codes (DTCS)
(see page 11-3), and make sure the ECM has no
malfunction.
Note these items before trou bleshooting:
. Due to the action of the immobilizer system, the
engine takes slightly more time to start than on a
vehicle without an immobilizer system.. When the system is normal, and the proper key is
inserted, the indicator light comes on for 2 seconds,
then it will go off.. If the indicatorstartsto blink after 2 seconds, or if the
engine does not start. remove any other immobilizer
keys or large key fobs on the key ring, then repeat the
starting procedure.
lf the engine still does not start, continue with thisprocedure.
1. Turn the ignition switch ON {ll) with proper key.
2. Check to see if the immobilizer indicator light
comes on.
Does the indicator light blink?
YES Disconnect the 7P connector from the
immobilizer control unit-receiver, then go to step 9.
NO Check for these problems, then go to step 3.
. Blown No. 9 (10A)fuse in the under-hood
fuse/relay box.I. An open in the wire between the gauge assembly
and the immobilizer control unit-receiver.l. A faulty immobilizer indicator light,I. An open in the wire between the gauge assembly
and the under-hood fuse/relay box.l
Remove the driver's dashboard lower cover (see
page 20-59).
Remove the steering column lower cover (see page
11-9).
l
-_--t
22-165
5. Disconnect the 7P connector (A)from the
immobilizer control unit-receiver (B),
Check for voltage between the immobilizer control
unit-receiver 7P connector No. 7 terminal and body
ground.
ls there battery voltage?
YES-Go to step 7.
NO Check for these problems;
. Blown No. 9 {10A)fuse in the under-hood fuse/
relay box.l. An open in the WHT/RED wire.l
Check for voltage between the immobilizer control
unit-receiver 7P connector No. 6 terminal and bodyground with the ignition switch ON {ll).
ls there battery voltage?
YES- Go to step 8.
NO Check for these problems:
. Blown No.6 (15A)fuse in the under-hood
fuse/relay box,I. Faulty PGM-Fl main relay 1,t. An open in the YEUBLK wire.l
1.
(cont'd)

t
2.
3.
lmmobilizer Control Unit-Receiver Replacement
'LRemove the driver's dashboard lower cover (see
page 20-59).
Remove the steering column covers (see page 17-
Disconnect the 7P connector (A) from the
immobilizer control unit-receiver (B).
5.
Remove the two screws and the immobilizer
control unit-receiver from the ignition key cylinder(c).
Install the immobilizer control unit-receiver in the
reverse order of removal.
After replacement, rewrite the unit with a Honda
PGM Tester, then check the immobilizer system.
JI
6.
-___-l-
22-167

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
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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.

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