2003 HONDA CIVIC body and 3P

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
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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
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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

PGM-FI System
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DTC Troubleshooting
DTC P0107: MAP Sensor Circuit Low Voltage
1. Turn the ignition switch ON (lli.
2. Check the MAP with the scan tool.
ls about 101 kPa (760 mmHg,30 in.Hg)or 2.9 V
indicated?
YES Intermittent failu re, system is OK at this time.
Check for poor connections or loose terminals at
the MAP sensor and at the ECM.I
NO-Go to step 3.
3. Turn the ignition switch OFF.
4. Disconnect the MAP sensor 3P connector.
5. Turn the ignition switch ON (lll.
6. lvleasure voltage between MAP sensor 3P
conneclor terminals No. 1 and No. 3.
1.
sGl{GRN/WHTI
Wire s de of femaleterminais
ls there about 5 V?
YES Go to step 8.
NO-Go to step 7.
Measure voltage between EClvl connector
terminals 41 1 and 42'1.
ECM CONNECTOR A 13'IP}
MAP SENSOR 3P CONNECTOF
vccr{YEL/BED)
sGr{GRN/WHT}
11-52
Wire side of female terminals
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8.
ls there about 5 V?
YES-Repair open in the wire between the Eclvl(A21)and the MAP sensor.l
NO Update the ECM if it does not have the latest
software, or substitule a known-good ECM, then
recheck (see page 'l 1-6). lf the symptom/indication
goes away with a known-good ECfvl, replace the
original ECM.I
Check the MAP with the scan tool.
ls 2 kPa (15 mmHg,0.6 in.Hg) ot less or 0 V
ind icated?
YES-Go to step 9.
NO Replace the lvlAP sensor.l
Turn the ignition switch OFF.
Disconnect ECM connector A (31P).
Check for continuity between MAP sensor
connector terminal No. 2 and body ground.
MAP SENSON 3P CONNECTOA
ls therc continuity?
YES-Repair short in the wire between the ECM(A19) and the MAP sensor.l
NO Update the ECM if it does not have the latest
software, 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
9.
'10.
11.
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4.
DTC P0112: IAT Sensor Circuit Low Voltage
1. Turn the ignition switch ON (ll).
2. Check the IAT with the scan tool.
ls 302'F (150'C) or highet (or H-Limit in Honda
node of PGM Tester), ot 0 V indicated?
VES-Go to step 3.
NO Go to step 8.
Disconnect the IAT sensor 2P connector.
Check the IAT with the scan tool.
ls 302'F(150'C)or higher (or H-Limit in Honda
mode of PGM Testet), ot 0 V indicated?
YES-Go to step 5.
NO- Replace the IAT sensor.I
Turn the ignition switch OFF.
Disconnect ECM connector B (24P).
Check for continuity between IAT sensor 2P
connector terminal No. 2 and body ground,
IAT SENSOR2P CONNECTOR
,^ ,lr 2lt-l-----Tr---IAT_t{RED/YELI
II
Wire side of female terminais
ls there continuity?
YES Repair shon in the wire between the ECM
(B'17) and the IAT sensor.l
NO Update the ECM if it does not have the latest
software, 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
5.
6.
7.
8. Check the temperature reading on the scan tool.
Be aware that if the engine is warm, the reading
will be higher than ambient temperature. lI the
engine is cold, the IAT and ECT will have the same
va lue.
ls the correct ambient temperature indicated?
YES lntermittent failure, system is OK at this time
Check for poor connections or loose terminals at
the IAT sensor and at the ECM.I
NO Replace the IAT sensor.l
11-55

PGM-FI System
DTC Troubleshooting (cont'dl
DTC P0122: TP Sensor Circuit Low Voltage
1. Turn the ignition switch oN (111.
2. Check the throttle position with the scan tool.
ls there about 10./. or 0.5 V when the thrcttle is
fully closed and about 90% or 4.5 V when the
throttle is fully opened?
YES Intermittent failure, system is OK at this time.
Check for poor connections or loose terminals at
the TP sensor and at the ECM. t
NO Go to step 3.
3. Turn the ignition switch OFF,
4. Disconnect the TP sensor 3P connector.
5. Turn the ignition switch ON (ll).
6. Measure voltage between the TP sensor 3P
connector terminals No. 1 and No. 3.
TP SENSOR 3P CONNECTOR
Wire side of female terminals
ls there about 5 V?
YES-Go to step 7.
NO Go to step 14.
Turn the ignition switch OFF.1.
11-60
8. At the sensor side, measure resistance between the
TP sensor 3P connector terminals No. 1 and No. 2
with the throttle fully closed.
TP SENSOR 3P CONNECTOR
Terminal side of male terminals
Is there about 0.5 0.9 kQ ?
YES Go to step 9.
NO Replace the throttle body (the TP sensor is not
available separately). I
Measure resistance between the TP sensor 3P
connector terminals No. 2 and No. 3 with the
throttle fully closed.
TP SENSOR 3P CONNECTOB
Terminal side of male terminals
ls there about 4.5k{l ?
YES Go to step 10.
NO Replace the throttle body (the TP sensor is not
available separately). I
10. Disconnect ECM connector A (31P).
9.\

11. At the wire harness side, check for continuity
between TP sensor 3P connector terminal No, 2
and body ground.
TP SENSOR 3P CONNECTOR
1 1213
'PS
REO
Wire side ot Iemale terminals
ls thete continuity?
YES-Repair short in the wire between the ECM
{A15) and the TP sensor.ll
NO-Go to step 12.
Connect ECM connector terminal A15 to body
ground with a jumper wire.
ECM CONNECTOR A 131P)
1121345679
1011112tc68 19 t2021
2312428129130
,tf$,rr*, ] ;uueen wrne
Wire side oJ .female terminals
/BLKI
12.
13. At the wire harness side, check for continuity
between TP sensor 3P connector terminal No. 2
and body ground.
TP SENSOR 3P CONNECTOR
(RED/BLX}
Wire side of female terminals
ls there continuity?
YES-Update the ECM if it does not have the latest
software, 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 ECM
(A15) and the TP sensor.l
14. lvleasure voltage between ECM connector
terminals 410 and A20.
ECM CONNECTOB A 131P}
vcc2(YEL/8LU)
Wire side of female terminals
ls there about 5 V?
YES Repair open in the wire betlveen the ECM
(A20) and the TP sensor.I
NO Update the ECM if it does nor have the latest
software, or substilute a known-good ECM, then
recheck (see page 1 1-6). lf the symplom indication
goes away with a known-good ECM. replace lhe
original ECM.I
123
TPS
11-61