2003 HONDA CIVIC Workshop Manual

ldle Control System
DTC Troubleshooting
DTC P0505: ldle Control System Malfunction
NOTE: lf DTC P1519 is stored atthe same time as DTC
P0505, troubleshoot DTC P1519 first, then recheck for
DTC P0505.
1. 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,
2. Checkthe engine speed at idle with no,load
conditions: headlights, blower fan, rear defogger,
radiator fan, and air conditioner off.
Is the engine running at 750t50 rpm?
YES - Intermittent failure, system is OK at this
trme.I
NO lf the idle speed is less than 700 rpm, go to
step 3; if it's 800 rpm or higher, go to step 4.
3. Disconnect the idle air control {lAC) valve3P
connector.
Does the engine speed increase or fluctuate?
YES- Check the idle speed {see page 1 1-138). lf the
idle will not adjust properly, clean the passage in
the throttle body, and then adjust the idle. I
NO- Replace the IAC valve.I
4. Turn the ignition switch OFF.
5. Remove the intake air duct from the throttle body.
6. Start the engine, and let it idle.
11-130
(
7. Put your fingers on the lower pon (A) inthethrottle
oooy.
Does the engine stall?
YES Checkthe idle speed (see page 11-138). lfit's
out of specification, replace the IAC valve.l
NO With the throttle valve completely closed,
check for vacuum leaks, and repair as necessary.l

DTC Pl519: IAC Valve Circuit Malf unction
1. Resetthe ECM (see page 11-4).
2. Turn the ignition switch ON (ll)
ls DTC P 1519 indicated?
YES Go to step 3.
NO-lntermittent failure, system is OK at this time.
Check for poor connections or loose terminals at
the IAC valve and at the ECM.I
3. Turn the ignition switch OFF.
4. Disconnect the IAC valve 3P connector.
5. Turn the ignition switch ON (ll).
6. Measure voltage betlveen IAC valve 3P connector
terminal No. 2 and body ground.
IAC VALVE 3P CONNECTOR
IGP {YEL/BLK)
Wire side of female terminals
ls there battery voltage?
YES Go to step 7.
NO-Repair open in the wire between the IAC valve
and the PGM-Fl main relay 1.1
Turn the ignition switch OFF.
123
7.
8, Check for continuity between body ground and IAC
valve 3P connector terminal No. 1.
IAC VALVE 3P CONNECTOR
123
PG1 {BLK}
a.
Wire side of lemale terminals
Is there continuity?
YES-Go to step 9.
NO Repair open in the wire between the IAC valve
and G'101.1
Disconnect ECM connector A (31P)
Check for continuity between body ground and
ECM connector terminal A12.
ECM CONNECTOR A 131P)
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IACV {BLK/RED}
1,)
Wire side oJ Jemale terminals
ls there continuity?
YES-Repair short in the wire between the IAC
valve and the ECM (A12).1
NO Go to step 1 1.
9.
10.
LCOnI Ol
11-131

ldle Control System
(DTC Troubleshooting (cont'd)
11. Connect IAC valve 3P connector terminal No.3 to
body ground with a jumper wire.
IAC VALVE 3P CONN€CTOR
IACV IBLK/REO}
JUMPER WIRE
Wire side of female terminals
Check for continuity between ECM connector
terminalAl2 and body ground.
ECM CONNECTOR A 131P)
Wire side of female terminals
ls there continuity?
YES Go to step 13.
NO-Repair open in the wire between the IAC valve
and rhe EcM (A12).r
Reconnect the IAC valve 3P connector.
Turn the ignition switch ON (ll).
13.
14.
11-132
15. Measure voltage between body ground and ECM
connector terminal A12.
ECM CONNECTOR A 131P}
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IACV IBLK/RED)
Wire side ol female terminals
I s there battery voltage?
YES-Update the ECI\4 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 ECI\4.1
NO-Replace the IAC valve.I!

A/G Signal Circuit Troubleshooting
Turn the ignition switch ON (ll).
Momentarily connect ECM connector terminals 424
and E18 with a jumper wire several times.
1.
2.
5.
Wire side of female terminals
ls there a clicking noise I rom the NC compressor
clutch?
YES Go to step 3.
NO-Go to step 6.
Sta rt the engine.
Turn the blower switch ON.
Turn the Ay'C switch ON.
Does the NC operate?
YES-The air conditioning signal is OK.I
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 €CM.l
6. Momentarily connect under-hood tuse/relay box
14P connector terminal No. 10 to body ground with
a jumper wire several times.
UNDER.HOOD FUSE/RELAY BOXI4P CONNECTOR
12356
1891011IJ14
ACC (RED)
JUMPER WIRE
Wire side of female terminals
ls there a clicking noise f rom the NC compressor
clutch?
YES- Repair open in the wire between the ECM(E'18) and the Ay'C clutch relay.l
NO- Check the A/C system for other symptoms.l
11-133

ldle Gontrol System
't.
Alternator FR Signal Circuit Troubleshooting
Disconnect the alternator 4P connector from the
alternalor.
Turn the ignition switch ON {ll).
Measure voltage between ECM connector
terminals 424 and 813.
ECM CONNECTORS
2.
3.
A l31Pl
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L(BRN/YEL)
ALTF(WHT
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89ltal,/l/15
Wire side of female terminals
ls there about 5 V?
YES Go to step 4.
NO-Go to step 13.
4. Turn the ignition switch OFF.
5. Reconnect the alternator 4P connector.
6. Slan 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. lvleasure voltage between ECM connector
terminals A24 and B 13.
Does the voltage decrease when the headlights
and rear window defogger arc tutned on?
YES The alternator FR signal is OK.l
NO-Go to step 8.
8. Turn the ignition switch OFF.
9. Disconnect ECM connector B (24P).
10. Disconnect the alternator 4P connector.
/REDI
11-134
'11. Connect alternator 4P con necto r term inal No.4 to
body ground with a jumper wire.
ALTERNATOR 4P CONNECTOR
12
ALTF34IWHT/RED)
JUMPER WIRE
12.
Wire side of female terminals
Check for continuity between body ground and
EClvl connector terminal 813.
ECM CONNECTOB B (24PI
Wire side of female terminals
ls there continuity?
YES-Testthe alternator (see page 4-22).1
NO Repair open in the wire between the ECM(B 13) and the alternator.l
Turn the ignition switch OFF.
Disconnect ECM connector B (24P).
\
13.
't 4.

15. Check for continuity between body ground and
ECIM connector terminal 813.
ECM CONNECTOR B I24P}
Wire side of female terminals
ls there continuity?
YES Repair short in the wire between the ECM
(813) and the alternator.l
NO Update the ECM if it does not have the latest
software, or substitute a known-good ECM, then
recheck lsee page 1 1-6). lf the symptom/indication
goes away with a known-good ECM, replace the
original ECM.I
Electrical Power Steering (EPSI
Signal Circuit Troubleshooting
Turn the ignition switch ON (ll).
l\4easure voltage between ECM connector
terminals 424 and E16.
1.
2.
3.
4.
5.
Wire side of female terminals
ls there battery voltage?
YES Go to step 6.
NO Go to step 3.
Start the engine.
Turn the steering wheel lo the full lock position.
l\4easure voltage between ECM connector
terminals A24 and E16.
ls there momentaty battery voltage?
YES The EPS signal is OK.t
NO Go to step 10.
6. Turn the ignition switch OFF.
7. Disconnect the EPS control unit 20P connector.
8. Turn the ignition switch ON (ll).
(cont'd)
11-135

ldle Control System
Electrical Power Steering (EPSI Signal Circuit Troubleshooting (cont'd)
9. Measure voltage between EPS control unitterminal
No.l7 and body ground.
EPS CONTROL UNIT 2OP CONNECTOR
Wire side of female terminals
ls there battety voltage?
YES-Substitute a known-good EPS control unit
and recheck.I
NO- Repair open in the wire between the ECM(E 16) and the EPS control unit.l
Turn the ignition switch OFF.
Disconnect the EPS control unit 20P connector.
Turn the ignition switch ON (ll).
10.
I 'I.
12.
11-136
'13. l\4easure voltage between EPS control unitterminal
No. 17 and the body ground.
EPS CONTROL UNIT 2OP CONNECTOR
Wire side of female terminals
ls there battery voltage?
YES Substitute a known-good EPS control unit
and recheck.l
NO-Go to step 14,
Turn the ignition switch OFF.
Disconnectthe ECM connector E {31P).
Check for continuity between body ground and
ECI\4 connector terminal E16.
ECM CONNECTOR E {31PI
14.
t5_
16.
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2223zi ./29 30ol
EPSLD{LT GRN/BLK)
a,
Wire side ot Iemale terminals
lsthere continuity?
YES Repair short in the wire between the ECN4(E 16) and the EPS control unit.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/indicationgoes away with a known-good ECM, replace the
original ECM.I

Brake Pedal Position Switch Signal Circuit Troubleshooting
1. Check the brake lights.
Are the brake lights on without pressing the brakepedal?
YES Inspectthe brake pedal position switch(see page 19-6).I
NO Go to step 2.
2. Press the brake pedal.
Do the brake lights come on?
YES-Go to step 3.
NO Go to step 4.
3. Measure voltage between ECM connector
terminals A24 and E22 with the brake pedal
presseo.
ls there battery voltage?
YES-The brake pedal position switch signal is
oK,I
NO Repair open in the wire between the Eclvl(E22) and the brake pedal position switch.l
Wire side of lemale terminals
4. Inspect the No. 7 HORN, STOP (15A) fuse ln the
under-hood fuse/relay box.
ls the tuse OK?
YES- Repair open in the wire between the brake
pedal position switch and the No.7 HORN, STOP( l5A) fuse, Inspect the brake pedal position switch(see page 19-10).1
NO Repair short in the wire between the ECM(E22) and the No.7 HORN, STOP (15A)fuse.
Replace the No.7 HORN, STOP (15A)fuse.t
11-137