2003 HONDA CIVIC Ignition switch

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
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PGM-FI System
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DTC Troubleshooting (cont'dl
DTC P0113: IAT Sensor Circuit High Voltage
1. Turn the ignition switch ON (ll).
2. Check the IAT with the scan tool.
ls 4'F (-20'C) or less (or L-Limit in Honda
mode ot PGM Tester) or 5 V indicated?
3.
4.
YES-Go to step 3.
NO Intermitent failure, system is OK at this time.
Check for poor connections or loose terminals at
the IAT sensor and at the ECM.I
Turn the ignition switch OFF.
Disconnect the IAT sensor 2P connector.
Connect IAT sensor 2P connector terminals No. 1
and No. 2 with a jumper wire.
IAT SENSOR 2P CONNECTOR
rJ-- :---
l'lLl-'_-l--_----r--_
sG2 I rAT{GRN/YEL) I IRED/YEL)
L]JUMPER WIRE
Wire side of female terminals
6. Turn the ignition switch ON {ll).
11-56
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7. Check the IAT with the scan tool.
ls - 4"F ( 20'C) or less (or L-Limit in Honda
mode ot PGM Tester) or 5 V indicated?
YES Go to step 8.
NO - Replace the IAT sensor.l
8. Turn the ignition switch OFF.
9. Remove the jumper wire.
10. Connect ECM connector terminals A10 and 817
with a jumper wire.
ECM CONNECTORS
A (31 P)B {24 P)
Wire side of female terminals
Turn the ignition switch ON (ll).
Check the IAT with the scan tool.
ls - 4"F ( 20"C) or less (or L-Limit in Honda
mode of PGM Tester) or 5 V indicated?
YES Update the ECM if it does not have the latest
software, or substitute a known-good ECI\4 then
recheck (see page 11-6). lf the symptom/indicationgoes away with a known-good ECM. replace the
original ECM. !
NO Repair open in the wire between the ECM(A10, 817) and the IAT sensor.I
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11.
12.
JUMPER WIRE

PGM-FISystem
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DTC Troubleshooting (cont'dl
DTC P0117: ECT Sensor Circuit Low Voltage
1. Turn the ignition switch ON (ll).
2. Check the ECT with the scan tool.
ls 150'C (302'F)or higher (ot H-Limit in Honda
mode of PGM Tester) or 0 V indicated?
YES Go to step 3.
NO Intermittent failure, system is OK at this time.
Check for poor connections or loose terminals at
the ECT sensor and at the ECM. t
3. Disconnect the ECT sensor 2P connector.
4. Check the ECT with the scan tool.
ls 150'C (302"F)or higher (ot H-Limit in Honda
mode ot PGM Tester) or 0 V indicated?
YES-Go to step 5.
NO Replace the ECT sensor. !
5. Turn the ignition switch OFF.
6. Disconnect ECM connector B (24P).
11-58
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7. Check for continuity between the ECT sensor 2P
connector terminal No. 1 and bodv oround.
ECT SENSOR 2P CONNECTOR
Wire side of female terminals
ls there continuity?
YES-Repair short in the wire between the ECM(B8) and the ECT 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 EClvl, replace the
original ECM.I

DTC P0118: ECT Sensor Circuit High Voltage
1. Turn the ignition switch ON (ll).
2. Check the ECT with the scan tool.
ls 20'C ( 4'F)or less (or L-Limit in Honda
mode of PGM Tester) or 5 V indicated?
?
5.
YES Go to step 3.
NO lntermittent failure, system is OK at this time.
Check for poor connections or loose terminals at
the ECT sensor and at the ECM. I
Turn the ignition switch OFF.
Disconnect the ECT sensor 2P connector.
Connect the ECT sensor 2P connector terminals
No. 1 and No. 2 with a jumper wire.
ECT SENSOR 2P CONNECTOR
\
ltltltt.l
Ecr
-I-l*,
(RED/WHT) {GRN/YEL)
tlJUMPER WIRE
wire side oI Iemale terminals
6. Turn the lgnition switch ON (ll).
1.
8.
9.
10.
Check the ECT with the scan tool.
ls 20"C ( 4"F)or less (or L-Limit in Honda
mode ot PGM Tester) or 5 V indicated?
YES-Go to step 8.
NO Replace the ECT sensor.I
Turn the ignition switch OFF.
Remove the jumper wire.
Connect ECM connector terminals A10 and Bg with
a jumper wire.
ECM CONNECTORS
a {31 P}B {24 P)
Wire side of female terminals
Turn the ignition switch ON (ll).
Check the ECT with the scan tool.
ls 20"C ( 4"F) or less (or L-Limit in Honda
mode of PGM Tester) ot 5 V indicated?
YES - Update the ECM if it does not have the latest
software, or substitute a known-good ECI\4, then
recheck (see page 1 1-6). If the symptom/indication
goes away with a known-good ECM, replace the
original ECM.I
NO Repair open in the wire between the ECM
(A10, 88) and the ECT sensor.l
11.
12.
JUMPER WIRE
11-59

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.\

PGM-FI System
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DTC Troubleshooting (cont'd)
DTC P0123: TP Sensor Circuit High Voltage
1. Turn the ignition switch oN (ll)
2. Check the throttle position with the scan tool.
ls there about 10% or 0.5 V when the throttle is
fully closed and about 90% or 4.5 V when the
throttle is f ully opened?
YES lntermittent failure. system is OK at this time.
Check for poor connections or loose terminals at
the TP sensor and at the ECM, I
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. At the wire harness side, measure voltage between
the TP sensor 3P connector terminals No. 1 and
No.3.
TP SENSOR 3P CONNECTOR
W;re side of female terminals
ls thete about 5 V?
YES-Replace the throttle body (the TP sensor is
not available separately). I
NO Go to step 7.
11-62
7. Measure voltage between ECM connector
terminals A10 and A20.
ECM CONNECTOR A 131PI
Wire side of female terminals
Is there about 5 V?
YES- Repair open in the wire between the ECM(A10) and the TP sensor. t
NO Update the ECM if it does not have the latest
soflware, or substitute a known-good ECM, then
recheck (see page 11-6). lf the symptom/indicationgoes away with a known-good ECM, replace the
original ECM.I

DTC Pl121: TP Sensor Signal Lower Than
Expected
1. Turn the ignition switch ON (ll).
2. Check the throttle position with the scan tool.
ls 12.9'/.,0.6 V, or higher indicated when the
throttle is tully opened?
YES- Intermittent failure, system is OK at this
time.I
NO-Replace the TP sensor (the TP sensor is not
available separately). I
DTCP1122:.fP Sensor Signal Higher Than
Expected
1. Turn the ignition switch ON (ll).
2. Check the throttle position with the scan tool.
ls 12.9 %,0.6 V, or less indicated when the throttle
is f ully closed?
YES Intermittent failure, system is OK at this
time.l
NO Replace the TP sensor (the TP sensor is not
available separately). I
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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.
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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