2003 HONDA CIVIC Circuit

'10. Check continuity between the ECM connector
terminal 810 and body ground.
ECM CONNECTOR S I24PI
23 t4 t567
8I10,/1,/315
118,Nnt,/2123
ACGL (WHT/BLUI
t1'
Wire side ol female terminals
ls there continuity?
YES- Repair short to ground in the wire between
the ECM and the engine wire harness 6P connector.
t
NO-Go to alternator and regulator test.
Alternator and Regulator Circuit Test
1. Be sure the battery is sufficiently charged and in
good condition {see page 22-50), and the
connections at the fuse box and alternator are
clean and tight.
2. Raise the hoist to full height.
3. Hook up the ammeter, 0 400 A, to the starter
sub harness.
Lower the hoist.
Hook up the voltmeter, 0 20 V (accurate within
0.1V),toT101.
(cont'd)
4-23

Gharging System
Charging Circuit Troubleshooting (cont'd)
6. Start the engine. Hold the engine at 3,000 rpm with
no load (in Neutral) until the radiator fan comes on,
then let it idle.
7. Raise the engine speed to 2,000 rpm, and hold it
there.
8. Turn the headlights (high beam) on, and measure
voltage at the under-hood fuse/relay box terminal.
ls the voltage between 13.9 and 15.1 v?
YES-Go to step 9.
NO Repair or replace the alternator components
(see page 4-30).1
9. Read the amperage at '13.5 V.
NOTE: Adjust the voltage by turning the blower
motor, rear window defogger, brake lights. etc. ON.
ls the amperage 604 ot morc?
YES-Alternator/regulator operation is OK. I
NO Repair or replace the alternator components(see page 4-30).1
4-24
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Alternator Control System Test
NOTE: After troubleshooting, perform the engine
control module (ECM) idle learn procedure (see page
11-139).
1 . Check for proper operation of the electrical load
detector (ELD) by checking the malfunction
indicator lamp (MlL) (see page 1 l-3). lf a DTC is
present, diagnose and repair the cause before
continuing with this test.
2. Disconnect the engine wire harness 6P connector
from the starter sub harness 6P connector.
3. Start the engine, and turn the headlights (high
beam) ON,
4. Measure voltage between the engine wire harness
6P connector terminal No. 2 and the positive
terminal of lhe battery.
C {WHT/GRN)
ENGINE WIRE HARNESS 6P CONNECTOR
Wire side of female terminals
ls there 1 V or less?
YES Go to step 8.
NO-Go to step 5.
Turn the headlights and ignition switch OFF.
Disconnect ECM connector B (24P).
5.
6.
BATTERY

Circuit Diagram
' No.aloAl USAnod.lNo.20 itoAl C.md! modrlUISEF NOOD fUS'/iILAY IOX
-to ots BU/YIL
lcl H0Tii0llilllmdSTARTlllll
1 Honilsffroi
CTuICII PEDALP0sm0 swtrct
26 1113cnu6E coNTnoL uNtT l0
4-37

Cruise Control
Symptom Troubleshooting Index
NOTE:' The numbers in the table showthetroubleshooting sequence.. Before troubleshooting.- check the No, 10 (7.5A) and No. 4 (10A) fuses in the under-dash fuse/relay box. and the No. 7 (15A) fuse in theunder-hood fuse/relay box,- check that the horn sounds.- check the tachometer to see if it works properly.- check the speedometer lo see if it works properly.
SymptomDiagnostic procedureAlso check forCruise control cannot be
set
1. Check main switch (see page 4-42)
2. Check SET/RESUME/CANCEL switch (see page 4-42)
3. Test brake pedal position switch (see page 22-84) and checkits adjustment {see page 19,6)
4. Test clutch pedal position switch (see page 4-45) and check
its adjustment (see page 12-41
5. Check cruise control unit {see page 4-40}
6. Check vehicle speed sensor (VSS) (see page 22-65)
. Poor ground:
G501. Open circuit,
loose or
disconnected
term inals:
LT GRN,
BLI(ORN.
GRY/RED, BLU.
LT BLU,
BLUAA/HTCruise control can be set
but indicator light does
not go on
1. Check cruise control indicator bulb in gauge assembly {seepage 22-631
2. Check cruise control unit (see page 4-40)
. Poor ground:
G501. Open circuit,
loose or
disconnected
termrnats:
YEL, BLUA/ELar, 'i.a c^aa.l ic
noticeably higher or
lower than what was set
1. Check vehicle speed sensor (VSS) {see page 22-65)
Check cruise control actuator {see page 4-43)
2. Check cruise control unit (see page 4-40)
Excessive overshooting
or undershooting when
trying to set speed
1. Check cruise control actuator (see page 4-43)
2. Check vehicle speed sensor (VSS) (see page 22-65)
Check cruise control unit (see page 4-40)
3.
Speed fluctuation on a
flat road with cruise
control set
1. Check vehicle speed sensor (VSS) (see page 22-65)
Check cruise control actuator (see page 4-43)
2. Check cruise control unit (see page 4-40)
Vehicle does not
decelerate or accelerate
accordingly when SET/
RESUME/CANCEL button
is pushed
1. Check SET/RESU ME/CANCEL switch (see page 4-42)2. Check cruise control unit {see page 4-40)
Open circuit, loose
or disconnected
terminals:
GRY/RED,
LT GRN/BLKSet speed does not
cancel (engine rpm stays
high) when clutch pedal
is pushed
1. Testclutch pedal position switch (see page 4-45) and checkits adjustment (see page 12-4)
2. Check cruise control unit (see page 4-40)
Short to ground in
the LT BLU wire
Set speed does not
cancel when brake pedal
is pushed
'1. Test brake pedal position switch (see page 22-84) and checkits adjustment (see page 19-6)
2. Check cruise control unit (see page 4-40)
Open circuit, loose
or disconnected
terminals:
WHT/BLK
4-38
g,

svmptomDiagnostic procedureAlso check for
Set speed does not
cancel when main switch
is oushed OFF
1. Check main switch (see page 4-42)
2. Check cruise control unit (see page 4-40)
Short to power in
the LT GRN wire.
Set speed does not
cancel when CANCEL
button is pushed
1. Check SET/RESU ME/CANCEL switch (see page 4-42)
2. Check cruise control unit (see page 4-40)
Open circuit, loose
or disconnected
terminals:
GRYiRED,
LT GRN/BLK
Set speed will not
resume when RESUME
button is pushed (with
main switch on, and set
speed temporarily
cancelled by pressing the
brake Dedal)
1. Check SET/RESU ME/CANCEL switch (see page 4-42)
2. Check cruise control unit {see page 4-40)
Open circuit, loose
or disconnected
terminals:
LT GRN/BLK
4-39

Engine Cooling
Cooling System
Component Location Index ......................................... 10-2
Radiator Cap Test ..................... .......... 10-3
RadiatorTest ............. 10-3
Fan Motor Test .......... l0-4
Thermostat Test ...................... ........... 10-4
Water Pump Inspection ..................... 10-5
Water Pump Replacement ................. 10-5
Coolant Check .............. ....................... 10-6
Coolant Replacement ......................... 10-6
Thermostat Replacement .................. 10-8
Water Passage Installation ................ 10-9
Water Outlet Installation .................... 10-9
Radiator and Fan Replacement ................................... 10-10
Fan Controls
Component Location Index ......................................... 10-11
Symptom Troubleshooting Index ............................... 10-12
Circuit Diagram ......... 10-13
Radiator Fan CircuitTroubleshooting ........................ 10-14
Radiator Fan Switch Circuit Troubleshooting
(Open) ............ ........ 10-16
Radiator Fan Switch Circuit Troubleshooting
(Short) ............ ........ 10-16
Radiator Fan Switch Test ................... 10-17
Radiator Fan Switch Reolacement .............................. 10-17

Fan Controls
Symptom Troubleshooting Index
Before performing any troubleshooting procedures check:. Fuses. Grounds. Cleanliness and tightness of all connectors
\{
\,4
SYMPTOMPROCEDURE
Radiator fan does not run at allRadiator Fan Circuil Troubleshooting (see page 1O-14).
Radiator fan does not run for engine cooling, but it runswith A,/C ON
Radiator Fan Switch Circuit Troubleshooting (Open)
(see page 10-16).
Radiator fan runs with ignition switch ON (ll), Ay'C OFF,
and engine temperature below 199"F (93"C)Radiator Fan Switch Circuit Troubleshooting (Short)
(see page 10-'16).
10-12
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oCircuit Diagram
UIIDEF HOOD FJSE/NILAY BOX
' No.20loA) : USA moddNo.20l50A) : Cm.de mod.l
UNDEN DASXFUSE/RELAY BOX
lG2H0TiiAClill,0N{lllrndSTABI llll)
10-13