2003 HONDA CIVIC Engine temperature coolant sensor

lgnition Timing Control
The ECM contains the memory for basic ignition timing
at various engine speeds and manifold absolute
pressure. lt also adjusts the timing according to engine
coolant temperature.
Iniector Timing and Duration
The ECM contains the memory for basic discharge
duration at various engine speeds and manifold
pressures. The basic discharge duration, after being
read out from the memory, is further modified by
signals sent from various sensors to obtain the final
discharge duration.
By monitoring long term fuel trim, the ECM detects long
term malfunctions in the fuel system and sets a
Diagnostic Trouble Code {DTC).
Intake Air Temperature (lAT) Sensor
The IAT sensor is a temperature dependent resistor
{thermistor). The resistance of the thermistor decreases
as the intake air temDerature increases.
Knock Sensor
The knock control system adjusts the ignition timing to
minimize knock.
PIEZOCERAMIC
Malfunction Indicator Lamp lMlLl Indication {ln relation
to Readiness Codes)
The vehicle has certain "readiness codes" that are part
of the on-board diagnostics for the emissions systems.
lf the vehicle's baftery has been disconnected or gone
dead. if the DTCS have been cleared, or if the ECM has
been reset. these codes are set to incomplete. In some
states, part of the emissions testing is to make sure
these codes are set to comDlete. lf all of them are not
set to complete, the vehicle may fail the test and the
test cannot be finished.
To check if the readiness codes are set to complete,
turn the ignition switch ON (ll). but do not start the
engine.TheMILwill comeonforlS 20seconds. lf it
then goes off, the readiness codes are set to complete,
lf it blinks severaltimes, one or more readiness codes
are not set to comolete. To set each code, drive the
vehicle or run the engine as described in the
procedures to set them in this section (see page 1 1-46).
Manifold Absolute Pressure {MAP) Senso]
The MAP sensor converts manifold absolute pressure
into electrical signals to the ECM.
SENSOR UNIT
(cont'd)
11-27

Fuel and Emissions Systems
System Descriptions (cont'dl
ldle Control System Diagram
The idle speed of the engine is controlled by the ldle Air Control (lAC) varve:
'Aftertheenginestarts,theIACvalveopensforacertainamountoftime.Theamountofairisincreasedtoraisethe
idle sDeed.. When the engine coolant temperature is low, the IAC valve is opened to obtain the proper fast idle speed. Theamount of bypassed air is controlled in relation to engine coolant temperature.
INTAKE MANIFOLDIAC VALVEAKE AIR DUCT
CLEANER
\
BLK/REO
YEL/BLK ---< FromPGM.FIMAINRELAY
THROTTLE AODY
Intake Air System Diagram
This system supplies air for engine needs. A resonator in the intake air
drawn into the svstem.
VARIOUSSENSOnS
pipe provides additional silencing as air is
THROTTLE AODYVARIOUSSENSORS
BLK
BLK
I
11-36
{

PGM-FI System
Component Location Index
CAMSHAFT POS]TION {CMP) SENSOR B(TOP DEAD CENTER (TDC}SENSORITroubleshootina. oaoe 1 1-95Replacement, p;ge 1-1.1 14
ELECTRICAL LOADDETECTOR {ELDITroubleshooting,page 1'l -92
INTAKE AIR TEMPERATURE{IATI SENSORTroubleshooting,page 'l'l-55
Replacement, page 11-'l 15
f- \
rl
KNOCK SENSORTroubleshooting, page 1 1-77Beplacement, page 11 115
ENGINE COOLANT TEMPERATURE(ECTI SENSORTroubleshooting, page 1 1-57Replacement, page 11 114
MANIFOLD ABSOLUTE PRESSURE(MAP) SENSORTroubleshooting, page 1 1-52
THROTTLE POSITIONITP} SENSORTroubleshooting, page 11-60CRANKSHAFT POSITIONICKPISENSORTroubleshooting, page'l 1-78Beplacement, page 1 1-'l 16
AIR FUEL RATIO {A/F)SENSOR ISENSOR 1}Trorrbleshooting, page 1 1-84Replacement, page 11- 1 13
{cont'd)
ii'- r'1
.I11 ---:,I''.!,i(..,.?:fir-J-
.....,..:--.
11-49

PGM-FI System
aDTG Troubleshootang (cont'dl
DTC P0128: Cooling System Malfunction
NOTE; lf the DTCS listed below are stored at the same
time as DTC P0128. troubleshoot those DTCS first, thenrecheck for P0128.
P0107, P0108, P1128, P1129: N4anifold absolutepressure (MAP) sensor
P] I06, P1 107, P1 108: Barometric pressure (BARO)
sensor
P1259: VTEC system
P01 16, P01 17, P01 18: Engine coolant temperature (ECT)
sensor
P01 12, P01 13: Intake air temperature (lAT) sensor
P0500: Vehicle speed sensor {VSS)P0335, P0336: Crankshaft position (CKP) sensor
P0300: Random misfire
P0301, P0302, P0303, P0304: No. 1, No. 2, No.3 or No.4
cylinder misfire
P0505: ldle control system malfunction
P1519: ldle air control (lAC)valve
DTC P0128 can occasionally set when the hood is
opened while the engine is running.
1. Check the engine coolant level
Is the engine coolant level low?
VES Refill the engine coolant. lf necessary, repair
the coolant leakage.l
NO Go to step 2.
2. Turn the ignition switch ON (ll), and make sure the
A,/C is off.
11-64
\
3. Check the radiator fan.
Does the tadiator fan keep running?
YES Checkthe rad iato r fan circuit (see page 10-
14), the radiator fan switch circuit (Short) (see page
10-'16), and the radiator fan switch (see page 10-17).
Also, inspect the ECT and IAT circuits and terminal
connections. lf the circuits, the switch, and the
connections are OK, update the ECI\4 if it does not
have the latest software. or substitute a known-good ECM, then recheck (see page 1 1-6). lf the
symptom/indication goes away with a known-good
ECM, replace the original ECM.I
NO Replace the thermostat (see page 10-8).1

EVAP System
DTC Troubleshooting (cont'dl
31. While monitoring FTP sensor voltage with theHonda PGM Tester, or measuring voltage betweenECM connector terminals E4 and E14, slowly pump
the vacuum oumD.
ECM CONNECTOR E 13lPI
Wire side ot female terminals
32. Continue to pump vacuum until the voltage drops
to about 1.5 V. Make sure the engine coolant
temperature is still above 95'F 135.C) and your
vacuum pump has no leak.
33. Monitor the voltage for 20 seconds.
Does the voltage drop 1.5V and hold for at least
20 seconds?
YES Inspect the EVAP canister vent shut valve
line and connections.l
NO-Go to step 34.
34. Turn the ignition switch OFF.
35. Discon nect the quick-con nect fitting (A) fromthe
EVAP canister, and plug the canister port {B).
36. Turn the ignition switch ON (ll).
11-184
42. Turn the ignition switch ON (ll).
I
38.
39.
37. While monitoring FTP sensor voltage with theHonda PGM Tester, or measuring voltage betweenECM connector terminals E4 and E 14, slowly pump
the vacuum pump.
ECM CONNECTOR E {31PI
Wire side of lemale terminals
Continue to pump vacuum until the voltage drops
to about 1.5V. Make sure the engine coolant
temperature is still above 95"F (35"C) and your
vacuum pump has no leak.
Monitor the voltage for 20 seconds
Does the voltage hold for at least 20 seconds?
YES Inspecl the fuel tank vapor control lineand
connections.I
NO Go to step 40.
Turn the ignition switch OFF.
Disconnect the purge line hose {A) from the
canister at the metal line and plug the hose (B).
40.
41.

43. While monitoring FTP sensor voltage with the
Honda PGM Tester, or measuring voltage between
ECM connector terminals E4 and E14, slowly pump
the vacuum pump.
ECM CONNECTOR E {31P)
Wire side of female terminals
Continue to pump vacuum until the voltage drops
to about 1.5V. Make sure the engine coolant
temperature is still above 95'F (35'C) and your
vacuum pump has no leak.
Monitor the voltage continuously for 20 seconds.
Does the voltage drop to 1.5 V and hold f or at
least 20 seconds?
YES Inspect the EVAP canister purge valve line
and connections. lf they are OK, perform the EVAP
two way valve test (see page 11-186) and the fuel
tank vapor control valve test (see page 1'l-187) l
NO-Replace the EVAP canister
(see page 11-189).1
44.
45.
11-185

Heating and Air Conditioning
Radiator and Condenser Fans
Common
(cont'dl
Circuit Troubleshooting
9. Using a Backprobe Set, measure the voltage
between the No. 6 terminal of ECN4 connector B
{24P) and body ground with the ECM connectors
connecteo.
ECM CONNECTOR B {24P}
ls there battery voltage?
YES UDdate the ECM if it does not have the latest
so{tware, or substitute a known-good ECM, then
recheck (see page 11-6). lf the symptom/indication
goes away with a known-good ECM, replace the
original ECM.I
NO Repair open in the wire between the radiator
fan relay, the condenser fan relay and the ECM. t
Wire side of female terminals
21-30
Compressor Clutch Circuit
Troubleshooting
1. Check the No. 1 (20A) fuse in the under-hood
fuse/relay box, and the No. 14 {10A)fuse in the
under-dash fuse/relay box.
Are the tuses OK?
YES Go to step 2.
NO Replace the fuse(s), and recheck.I
2. Check the engine coolant temperature, the throttleposition sensor, and the idle speed (use the Honda
PGM Tester PGM-Fl data list if possible).
ls the coolant temperaturc above nomal, the
throttle position sensor rcading too high, or the
idle speed too low?
YES Troubleshoot and repair the cause of the
high engine coolant temperature, high throttle
position sensor reading, or low idle speed.l
NO-Go to step 3.
3. Remove the compressor clutch relay from the
under-hood fuse/relay box, and test it (see page 22-
51 ).
ls the relay OK?
YES Go to step 4.
NO Replace the compressor clutch relay.I
4. Measure the voltage between the No. 2 terminal of
the compressor clutch relay 4P socket and body
ground.
\
COMPfiESSON CLUTCH BELAY 'P SOCKET
ls there battery voltage?
YES Go to step 5.
NO Replace the under-hood fuse/relay box.I

Connectors and Harnesses
Engine Wire Harness
Camshaft position (CMP) sensorLllr sensorEC[,4 connector AECI/l connector BEngine coolant temperature (ECT)
sensorEngine oil pressure switchEVAP canister purge valveldle air control (lAC)valve
lgnition coil No. llgnition coil No. 2lgnition coil No. 3lgnition coil No. 4Iniector No. 1Inlector No.2Iniector No.3Iniector No. 4Intake air temperature {lAT) sensor
TDC sensorThrottle position (TP) sensorVehicle speed sensor (VSSI
VTC oil control solenoid valveVTEC oil pressure switchVTEC solenoid valvec 101
c102
233
242
Transmission housingLeft side of engineRight side ofengineUnder glove boxUnder glove boxLeft side of engine
Bight side oI engineLeft side of intake manifoldLeft side of intake manifoldMiddle of engine compartmentMiddle of engine compartmentMiddle of engine compartmentMiddle of engine compartmentMiddle of engine compartmentMiddle of engine compartmentMiddle of engine compartmentMiddle of engine companment
28
1845672524201912
811102729303
22
12333332222233
322220
Left side of intake manifoldLeft side of engineLeft side of intake manifoldTransmission housingRight side o{ engineRight side of engineRight side of engineUnder right side of dash
Front of engine companment
Front of engine compartment
ECM wire harness {see page22-321Starter subharness (see page22-15)Starter subharness (see page22 151
Connector to Harness Index (cont'dl
22-16