Throttle HONDA CIVIC 2003 7.G User Guide

Fuel and Emissions Systems
Symptom Troubleshooting Index
When the vehicle has one of these symptoms, check the diagnostic trouble code (DTC) with the scan tool. lf there is no
DTC, do the diagnostic procedure for the symptom, in the sequence listed, until you find the cause.
SvmotomDiaqnostic procedureAlso check lor
Engine will not sta rt
(MlL works OK, no DTCS set)
1. Test the battery {see page 22-50).
2. Test the starter (see page 4-8).
3. Troubleshoot the fuel pump circult (see page 11
141).
Low compressron
No ignition spark
lntake air leaks
Locked up engine
Broken timing chain
Contaminated fuel
Engine will not start (MlL
comes on and stays on, or
never comes on at all, no
DTCS set)
Troubleshoot the l\4lL circuit (see page 1 '1-97).
Engine will not start
(immobilizer indicator stays
on or flashs)
Troubleshoot the immobilizer system (see page 22-165).
Hard starting(MlL works OK, no DTCS set)
1. Testthe battery (see page 22-50).
2. Checkthe fuel pressure (see page 11-145).
Low compression
Intake air leaks
Contaminated fuel
Cold fast idle too low(MlL works OK. no DTCS set)
1. Do the ECM idle learn procedure (see page 11-139).
2. Checkthe idle sDeed (see paqe 11-138).
Cold fast idle too high
(MlL works OK, no DTCS set)
Do the ECI\4 idle learn procedure (see page 1 1- 139).
Checkthe idle speed {see page 11-138).
Inspect/adjust the throttle cable (see page 1 '1-'163).
Inspect and test the throttle body {see page 1 1-160}.
']
2.
3.
ldle speed fluctuates
(MlL works OK, no DTCS set)
1. Dothe ECM idle learn procedure (see page 11-'139).
2. Check the idle speed (see page 11-138).
3, Inspecvadjust th e throttle cable (see page 11''163).
4. Insoect and test the throttle bodv (see paqe 11- 160)
Intake air leaks
After warming up, idle speed
is below specifications with
no load
{MlL works OK, no DTCS set)
1. Do the ECIVI idle learn procedure (see page 1 1- 139).
2. Troubleshootthe alternator FR signal circuit (see
page 11-'134).
3. InsDect and test the throttle bodv {see paqe 1 1-160).
Vacuum hose clogged/
cracked/poor
connectron
After warming up, idle speed
is above specifications with
no toao(MlL works OK. no DTCS set)
1. Do the ECM idle learn procedure {see page 1'j-139).
2. Troubleshoot the alternator FR signal circuit(see
page 11-134).
Low power
(MlL works OK, no DTCS set)
1. Check the fuel pressure(seepagell-145).
2. Inspect and test the th roftle body (see page 11-160).
3. Inspecvadjust the throttle cable (see page 11-'163).
Low compressron
Camshaft timing
problem
Engine oil levelprootem
Engine stalls(MlL works OK. no DTCS set)
1. Do the ECM idle learn procedure (see page 1'l'139).
2. Check the fuel pressure{seepagell-145).
3. Check the idle speed (see page I 1-138).
4. Troubleshootthe brake pedal position switch signal
circuit (see paqe 11-137).
lntake air leaks
Faulty harness and
sensor connections
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11-10
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Fuel and Emissions Systems
System Descriptions (cont'd)
ECM Data (cont'd)
w
DataDescriptionOpera'ting ValueFreeze Data
Fuel System
Status
Fuel system status is indicated as "open" or "closed".
Closed: Based on the A,/F Sensor output, the ECM
determines the airlfuel ratio and controls the amount of
injected fuel.
Open: lgnoring Ay'F Sensor output, the ECM refers to
signals from the throttle position {TP), manifold absolute
pressure (MAP), intake air temperature (lAT), barometric
pressure (BARO), and engine coolant temperature (ECT))
sensors to control the amount of iniected fuel.
At idle speed: closedYES
Short Term
FuelTrim
The airlfuel ratio correction coefficient for correcting the
amount of injected fuel when the fuel system status
is "closed." When the ratio is leaner than the
sloichiometric ratio, the ECM increases short term fuel
trim gradually, and the amount of iniected fuel increases.
The airlfuel ratio gradually gets richer, causing a lower
oxygen content in the exhaust gas. Consequently, the
short term fuel trim is lowered, and the ECM reduces the
amount of injected fuel.
This cvcle keeps the airlfuel ratio close to the
stoichiometric ratio when in closed loop status.
o.7 1.5YES
Long Term
Fuel Trim
Long term fuel trim is computed from short term fuel trim
and indicates changes occurring in the fuel supply system
over a long period.
lf long term fuel trlm is higher than 1.00, the amounl of
injected fuel must be increased. lf it is lower than 1.00, the
amount of injected fuel must be reduced.
0.8 1.2YES
Intake Air
Temperature
{IAT)
The IAT sensor converts intake air temperature into
voltage and signals the ECM. When intake air
temperature is low, the internal resistance ofthe sensor
increases, and the voltage signal is higher.
With cold engine:
Same as ambient
temperature and ECT
YES
Throttle
Position
Based on the accelerator pedal position, the opening
anole of the throttle valve is indicated.
At idle speed:
about 10 %
YES
lgnition
Timing
lgnition timing is the ignition advance angle set by the
ECM. The ECM matches ignition timing to driving
conditions.
At idle speed: 8" t 5"
|' tuL wnen rne >L)
service signal line is
jumped with the Honda
PGM Tester
NO
Calculated
Load Value
(cLV)
cLV is the enoine load calculated from IMAP data.At idle speed:
12 34%
At 2.500 rpm with no
toao:'t4- 34%
YES
11-14
\.,
ra

ECM Inputs and Outputs at Connector A (31P)
NOTE: Standard battery voltage is 12 V.
1AFS]TC2
]GP23IGPl^:^ I -:,6AFS+1
CKPIKS
'10
SG2t112ACV15TPST6AFS_18
VSS
19IVAP2Avcc221vccl
22
HTC+
23LG225CMPA
26CMPB(rDc)
27tGPts,l28rcPts329tGPts230GPLS 1
Wire side ol female terminals
Terminalnumb€rWho colorforminal nameDescriptionSignal
ELKAVHTAFSHTC (AIR FUEL RATIO(4./F)SENSOR HEATERCONTROL}
Drives Ay'F sensor heaterWith ignit'on switch ON {ll): battery voltageWith fully warmed up engine runnang: 0 V
2YEUBLKIGP2 (POWEB SOURCE)Power source for the ECMcircuitWith the ignition switch ON 1ll): battery voltageWith the ionition switch OFF: about 0 V3YEUBLKIGPl {POWER SOURCE)Power source for the ECMWith the ignition swatch ON {ll): battery voltageWith the ionition switch OFF: about 0 V4BLKPG2 (POWER GROUNDGround forthe ECM circuitLess than 1.0 V at all times5BLKPG1 (POWER GROUNDGround forthe ECM circuitLess than 1.0 V at all times6REDAFS + (AIR FUEL RATIO(A,/F}SENSOR, SENSOR 1+ stDE)
Detects Ay'F sensor{sensor 1) signal
18LUCKP (CRANKSHAFTPOSITION SENSOR)Detects CKP sensor signalWith engine running: pulses
9BED/BLU)K SENSOB)Detects knock sensor siqnalWith enqine knocking: pulses10YEL2 {SENSOR;ROUND);ROUND)Sensor qrounrLessthan 1.0V at elltimesG1 {SENSORSensor qroun(Lessthan 1.0V at alltimes12BLIVREDIACV (IDLE AIR CONTROL(IAC)VALVE)Drives IAC valveWith engine runningr duty controlled
RED/BLKTPS (THROTTLE POSITIONSENSOR)Detects TP sensor signalWith throttle fully open: about 4.8 VWith thronle fullv closed: ahout 0-5 VREDI/ELAFS (AIR FUEL RATIO(4,/F)SENSOR, SENSOB 1SIDE)
Detects !y'F sensor(sensor 1)signal
18WHT/GRNVSS (VEHICLE SPEEDSENSOR)Detects VSS signalWath ignition switch ON (lli and front wheelsrotating: cycles from about 0 V to about 5 V or
(cont'd)
11-19

Fuel and Emissions Systems
System Descriptions (cont'dl
ECM lnputs and Outputs at Connector E (31P}
L
u
1iMoFPR
2sr-{]zs3LG34SG3
6$1025HTC
1M RLY
8AFSHTCR
I
14FTP15ELD
16EPSLD
18ACC20Z/VBS21VSV
22BKSW23K-LINE24SEFMJ26NEP
21rMoCD
29scs30WEN31MIL
Wire side of female terminals
NOTE: Standard battery voltage is '12 V.
TerminalnumberWire colorferminal nameDescription Signal
GRNI/ELIMO FPR (IMMOBILIZERFLJEL PUMP RELAYIDrives PGM Fl main relay 20Vfor2 seconds after turning ignition switch ON{ll). then batterv voltaoe2WHT/REDSHO2S (SECONDARYHEATED OXYGEN SENSOR(SECONDARY HO2S),SENSOR 2r
Detects secondary HO2S{sensor 2) signalWith throttle Jully opened from idle with fullywarmed up engine: above 0.6VWith throttle quickly closed: below 0.4 V
3BRN/YELLG3 (LOGIC GROUND)cround forthe ECM/PCMcontrolcircuitLess than 1.0 V at all times
4PNKSG3 {SENSOR GBOUND)Sensor oroundLess than 1.0 V at all times5YEUELUVCC3 {SENSOR VOLTAGE)Provides sensor voltageWith ignition switch ON (ll): about 5 VWith ionition switch OFF: about 0 V6BLKATr'HTSO25HTC (SECONDARYHEATED OXYGEN SENSOR(SECONDARY H02S)HEATER CONTROL)
Drives secondary HO2SheaterWith ignition switch ON (ll): baftery voltageWilh fullv warmed up engine running: dul,controlled
1REDA/ELMRLY (PGM.FI MAINRELAY}Drives PGM-Flmain relay 1Power source forthe DTCWith ignition switch ON (ll): about 0 VWith ignition switch OFF: battery voltage
IORNAFSHTCR {AIR FUEL BATIO(Iy'F)SENSOR HEATERCONTROL RELAY)
Drives air fuel ratio sensorheater relayWith ignition swirch ON {ll): 0 V
IYEUBLKIGl (IGNITION SIGNAL)Detecrs ignition signalWith ignition switch ON (ll): battery voltageWith iqnition switch OFF: about 0 V't4LT GRNFIP lFUEL TANKPRESSURE (FTP) SENSOR)Detects FTP sensor signalWith ignition switch ON (ll) and fuel fill cap open:about 2.5 VGRN/REDELD (ELECTRICAL LOADDETECTOF)Detects ELD signalWith ignition swjtch ON itt):aOoutO.t V l-gV(deDendino on electrical load)LT GRN/8LKEPSLD (ELECIRICALPOWEB STEEBING LOADDETECT)
Detects Power steering loadsrgnalAt idle with steering wheel in straight aheadposition: about 0 VAt idle with steering wheelatfull lock: momentary
'18REDACC (Ay'C CLUTCH RELAY)Drives P,/C clutch relayWith compressor ON: about 0 VWith comoressor OFF: batterv voltaoe
11-22
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Fuel and Emissions Systems
(
(
(
System Descriptions (cont'dl
Secondary Heated Oxygen Sensor (Secondary HO2S)
The secondary HO2S detects the oxygen content in the
exhaust gas downstream of the three way catalytic
converter (TWC) and sends signals to the ECM which
checks the efficiency of the TWC. To stabilize its output,
the sensor has an internal heater. The secondarv HO2S
is installed in the TWC.
ztRcoNtaELEMENTSENSORTERMINALS
HEATERTERMINALS
Starting Control
When the engine is started, the ECM provides a rich
mixture by increasing injector duration.
Throttle Position ITP) Sensor
The TP sensor is a potentiometer connected to the
throttle valve shaft. As the throttle position changes, the
sensor varies the signal voltage to the ECM. The TP
sensor is not replaceable apart from the throftle body.
ELEMENTBRUSH HOLDER
gRUSH
11-28
Vehicle Speed Sensor (VSS)
The VSS is driven by the differential. lt generates apulsed signal from an input of 5 volts. The number ofpulses per minute increases/decreases with the speed
of the vehicle.
BEARING

Fuel and Emissions Systems
(
{
System Descriptions (cont'd)
ldle Control System
When the engine is cold, the Ay'C compressor is on, the
transmission is in gear, the brake pedal is pressed. thepower steering load is high, or the alternator is
charging, the ECIM controls current to the ldle Air
Control (lAC) valve to maintain the correct idle speed.
Refer to the System Diagram to see the functional
layout of the system.
Brake Pedal Position Switch
The brake pedal position switch signals the ECM when
the brake pedal is oressed.
Electrical Power Steering (EPS) Senser
The EPS sensor signals the ECM when the power
steering load is high.
ldle Air Control llACl Valve
To maintain the proper idle speed, the IAC valve
changes the amount of air bypassing the throttle body
in response to an electrical signal from the ECM.
From AIR To INTAKECLEANER MANIFOLD
IAC VALVE
11-32
Fuel Supply System
Fuel Cut-off Control
During deceleration with the throttle valve closed,
current to the injectors is cut off to improve fuel
economy at engine speeds over 1,030 rpm. Fuel cut-off
action also occurs when engine speed exceeds
6,900 rpm, regardless of the position of the throttle
valve, to protect the engine from over-rewing. When
the vehicle is stopped. the ECM cuts the fuel at engine
speeds over 6,500 rpm.
Fuel Pump Control
When the ignition is turned on, the ECM grounds the
PGM-Fl main relay which feeds current to the fuel pump
for 2 seconds to pressurize the fuel system, With the
engine running. the ECM grounds the PGM-Fl main
relay and feeds current to the fuel pump. When the
engine is not running and the ignition is on, the ECI\4
cuts ground to the PGM-Fl main relay which cuts
current to the fuel pump.
PGM-FI Main Relay 1 and 2
The PGM-Fl main relay consists of two separate relays.
Relay 1 is energized whenever the ignition switch is ON(ll) to supply battery voltage to the ECM power to the
injectors, and power for relay, Relay 2 is energized to
supply power to the fuel pump for 2 seconds when the
ignition switch is turned ON (ll), and when the engine is
runnrng.

Intake Air System
Refer to the System Diagram to see the functional
layout of the system.
Intake Air Bypass Control Thermal Valve
When the engine is running, the intake air bypass
control thermal valve sends air to the iniectors,
INJECTOR
Throttle Body
The throttle body is a single-barrel side draft type. lt
houses the TP senser and the IAC valve. The lower
portion of the IAC valve is heated by engine coolant
from the cylinder head.
IAC VALVE
{cont'd)
11-33

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
{

Evaporative Emissions (EVAP) Control
System Monitor and Readiness code
NOTE:
All readiness code are cleared when the batterV is
disconnected or when the ECM is cleared with the
OBD ll scan tool or Honda PGM Tester.
The enable criteria must be repeated if the intake air
temperature (lAT) drops lower than 36'F (20"C) from
its value at engine $an up.
Enable Criteria
At engine start up, ECT and IAT are higher than 32'F(0"C) , but lower than 95'F (35"C).
At engine start up, the ECT and IAT are within 12'F(7'C) of each other.
Procedure
1. Connect the scan tool to the vehicle's data link
connector (DLC), and bring up the tool's generic
OBD ll mode.
2. Start the engine.
3. Test-drive the vehicle under stop-and-go conditions
with short periods of steady cruise. After about
2.5 miles (1.6 km), the readiness code should
switch f rom incomplete to complete.
4. lf the readinesscode isstill setto incomplete, check
for a temporary DTC. lf there is no DTC, one or
more of the enable criteria were probably not met;
repeat the procedure.
Air Fuel Ratio (A/Fl Sensor Monitor and
Readiness Code
NOTE:. Do not turn the ignition switch off during the
orocedure.. All readiness codes are cleared when the baftery is
disconnected or when the ECM is cleared with the
OBD ll scan tool or Honda PGM Tester.
Enable Criteria
ECT at 140'F (60"C) or higher.
Procedure
1. Connect the scan toolto the vehicle's data link
connector (DLC), and bring up the tool's generic
OBD ll mode.
2. Start the engine.
3. Test-drive the vehicle under stop-and-go conditions
with short periods of steady cruise. During the
drive, decelerate (wirh the throttle fully closed) for
5 seconds. After about 3.5 miles (2.2 km). the
readiness code should switch from incomDlete to
complete.
4. lfthereadinesscodeisstill set to incomplete, check
for a temporary DTC. lfthere is no DTC, the enable
criteria was probably not meU repeat the procedure.
Air/Fuel Ratio (A/Fl Sensor Heater Monitor
Readiness Code
NOTE; All readiness codes are cleared when the battery
is disconnected or when the ECM is cleared with the
OBD ll scan tool or Honda PGM Tester,
Procedure'1. Connect the scan tool to the vehicle's data link
connector {DLC), and bring up the tool's generic
OBD ll mode.
2. Start the engine, and let it idle for 1 minute. The
readiness code should switch from incomplete to
comDlete.
3. lf the readiness code is still set to incomplete, check
for a temporary DTC. lf there is no DTC, repeat theproceoure.
(cont'd)
11-47

Fuel and Emissions Systems
a
a
How to Set Readiness Codes (cont'd)
Misfire Monitor and Readiness Code
. This readiness code is always set to available
because misfiring is continuously monitored.. l\4onitoring pauses, and the misfire counter resets, if
the vehicle is driven over a rough road.. Monitoring also pauses, and the misfire counter
holds at its current value. if the throttle position
changes more than a predetermined value, or if
driving conditions fall outside the range of any
related enable criteria,
Fuel System Monitor and Readiness Code
. This readiness code is always setto available
because the fuel system is continuously monitored
during closed loop operation.. Monitoring pauses when the catalytic converter,
EVAP control system, and Ay'F sensor monitors are
active.. Monitoring also pauses when any related enable
criteria are not being met. Monitoring resumes when
lhe enable criteria is again being met.
Comprehensive Component Monitor and
Readiness Code
This readiness code is always set to available because
the comprehensive component monitor is continuously
running whenever the engine is cranking or running.
11-48
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