1998 HONDA INTEGRA ZC engine

ldle Control System
System Description
The idle speed of the engine is controlled by the ldle Air Control (lAC) V8lve.
The valve changes the amount of air bypassing into the intake manifold in response to electric current controlled by the
ECM. When the IAC Valve is activated. the valve opens to maintain the proper idle speed.
81881 engine {B18Cl, B18C5 engines are similarl:
YELI - F.om PGM'FIBLK - MAIN RELAY
VARIOUS SENSORS
L
1 1-96

2.
1.
1.
2.
After the engine stans, the IAC valve opens for a certain time. The amount ol air is increased to raise the idle speed
about 150 - 300 rpm.
When the coolant temperature is low, the IAC valve is opened to obtain the proper fast idle speed. The amount of
bypassed air is thus controlled in relation to the engine coolant temperature.
IDLE SPEEDtrpm,
ENGINECOOLANT TEMPERATURE
140
50
104
40
-1 32
-20 0
176 ('F)
80 fcl
When the idle speed is out of specification and the scan tool does not indicate Diagnostic Trouble Code (DTC) P0505
or P'1508, check the following items:. Adiust the idle speed (see page '11-111)
' ALT FR signal (see page 11-101). Air conditioning signal {seepage'11-102)' Brake switch signal (seepagell-104)
. Starter switch signal (see page 11-1051. A,4 gear position signal (see page 1l 106) (A"/T)
. PSP switch signal (see page 11-108) (USA)
. Fast idle thermo valve (see page 11-110). Hoses and connections. IAC valve and its mounting O rings
ll the above items are normal, substitute a known-good IAC valve and readjust the idle speed (see page 'l I -1 1 l).
lf the idle speed still cannot be adjusted to specification (and the scan tool does not indicate DTC P0505 or P1508) after
IAC valve replacement, substitute a known-good ECM and recheck. lf symptom goes away, replace the original ECM.
11-97

ldle Control System
ldle Control System
i P0505 | fne scan tool indicates Diagnostic Trouble Code (DTC) P0505: ldle control system malfunction,
NOTE: ll DTC Pl508 is stored at the same time as DTC P0505, troubleshoor DTC P1508 first. then troubleshoot DTC P0505.
Possible Cause
. IAC valve mechanical malfunctiorr
. Fast idle thermo valve malfunction (A"/T)
. Throttle body clogged port, improper adjustment
. Intake manifold, gasket leakage
. Intake air hose loose, leakage
a Vacuum hoses leakage
. ECT sensor incorrect output
. Throttle Position sensor incorrect output
Troubleshooting Flowchart
Problem verification:1. Start the engine. Hold theengine at 3,000 rpm wath noload 1in Park or neutral) untilthe radiator fan comes on,then let it idle.2. With the scan tool, check thefollowing items.- Throttle position should beapprox. 10% with the throttle fully closed.Engine coolant tempera-ture should be 116 212F(80 - 100'c).lf they are not within thespec., repair the faulty sensor crrcuft,3 Check the engine speed atidle with no-load conditions:headlights, blower fan, reardefogger, radiator fan, and airconditioner are not operating,
- The MIL has been reported on.- DTC P0505 is stored.
ls it 750 t 50 rpm (81881,
818C1 engines), 800 I 50 rpm(818C5 engine)?
Intermittent failur6, svstsm is OKat this tim€.
ls it 550 rpm (81881,818C1
engines), 600 rpm {818C5enginelor less?
-98
(To page 11'99)(To page 11-99)

Chock th6 IAC vrlv.:Disconnect the 2P connector tromthe IAC valve.
ooes lhe engine speed droporlhe engine stall?
Adiu3t th. lb.r.l idle Bp..d lrocplgc 11-1111.lf it's impo3.iblo, clo.n tho portsin thc throftlc body.
Ch.ck th€ frtt idl. th.rmo vrlv.:1, Turn the ignition switch OFF.2. Remov€ th6 intake air ductfrom the throttle body.3. Slart the engine and let it idle.4. Put your finger on the lowerport in the thronle bodv.
Chack angina coobnt Lv.l and fo.ai. in th. cooling ry.l.m. It OK,r.place tha fatt ldla lftarmo valva.Does the engine speed drop?
Put your linger on the uppor portin the throttle body.
Chacl tor vrcuum leek3, m.lcilJa th6 throttlo valvo ir com-plotaly cloaad, rnd ropair aa nac-a3aatY,
ooes ihe engin6 speed drop?
Adiutt th€ idl. .p..d l..r p.g.11-1111. lf it'. impo3riblo, rcpl.c.thc IAC v.lvc.
{A/T model)----tLOWERPORT
L. _. _._. _. _. _.-l
IDLETHERMOVALVE
1 1-99

ldle Control System
Problem verification:'1. Do the ECM Feset Procedure.2. Sta rt the engine.
ldle Air Control (lAG) Valve
The scan tool indicates Diagnostic Trouble Code (DTC) P1508: A problem in the ldle Air Control (lAC) valve
crrcurt.
The IAC Valve changes the amount of air bypassing the throttle body in response to a current signal from the Eclvl in
order to maintain the proper idle speed.FTom AIB To INTAKECLEANER MANIFOLD
IAC VALVE CONNECTOR IC116}
YES
WIRE SIDE OF FEMALE TERMINALS
ECM CONNECTOR A {32PI
Check for an open or short in thewire IIACV line):1. Turn the agnition switch OFFand reconnect the IAC valve
2. Disconnect the ECM connector A (32P).
3. Turn the ignition swatch ON (ll).
4. M easu re voltage betweenbody ground and ECM connector terminal A12.
IACV {8LK/BLU}
tacv{BLK/BI-UI
The MIL has been reoorted on.OTC Pl508 is stored.
lntermittent failure, svstem is OKat this time. Check for ooor con-nections or loose wires at C116{lAC valvel and ECM.
ls DTC P1508 indicated?
Check tor an open in lhe wirellGPl line):1. Turn the ignition switch OFF.2. Disconnect the IAC valve con
3. Turn the ignition switch ON (ll).
4. Measure voltage betlveen bodyground and the IACV connectorterminalNo.2.
Repair open in the wire betweenIAC valve and PGM-FI main relav-ls there battery voltage?
Repair open or shon in the wi.ebetween ECM {A12l and lAc valve.ls there battery voltage?
Check the IAC velve function:Momentarily connect ECM con-nector terminals A12 and A10with a jumper wire several times.
Does the IAC valve click?
Substitute a known-good ECMand rocheck. lf symptom/indica-tion goes away. replace the origi-nal ECM.
','*',,'Llu.9', I l112 15 16 17 1a1o20/
l--12u1 z"-if1za-2"' . '1 .
910
t-r '21
Wire side of female terminals
JUMPER WIRE
1-100

This signals the ECM when the Alternator (ALT) is charging.
Alternator (ALT) FR Signal
Check lor a short in th€ wire {ALTF line):1. Oisconnect the ALT GRN 4P(3P)* connector from the ALT.2. Turn the ignition switch ON {ll).3. Measure voltage between ECMconnector terminals C17 and A9.
ECM CONNECTORSA t32Pt
LG1
c 13lPl
ALT F(WHT/FEDI
Wire side of female terminals
ALT GRN 4P CONN€CTOR {C119}
JUMPER WIRE
Wire side of female terminals
ALT GRN 3P CONNECTOB {C119)*
JUMP€RWIRE
Wire side ot female terminals
12 15 t6 rr t8 19I
?
oALT F(WHT/REOI
23aI10
t112t3t5l6r819 ,/21
./,/,/2a29
[,ALT FIWHT/RED)
12339
11 12l517 tla19 ,/21
Inspection of ALT FR Signal.
Check for a shon in the wire {ALTF line):1. Turn the ignition switch OFF.2. Disconnecl the negative baatery cable from the battery.3. Disconnect the ECM connectorc (31P).
4. Check for continuity betweenbody ground and ECM con-nector terminal C17.
ls there approx.5 V?
Check the operation ofthe ALT:1. Turn the;Onition switch OFF-2. Reconnect the ALT GRN 4P(3P)* connector to the ALT.3. Start the engine. Hold theengine at 3,000 rpm wkh noload {in Park or neutral) untilthe radiator fan comes on,then let it idle.4. Measure voltage bet/veen ECMcon nector termina ls C17 and A9.
Ropair short in the wir6 betweenth6 ECM (C17) and the ALT.
Substitute a known-good ECMand recheck. It prescribed voltagGis now available, replace th€ origi-nal ECM.
Does the voltage decrease whenheadlights and rear defogger areturned on?ALT FR signal is OK.
Check tor an open in the wire {ALTF line):1. Turn the ignition switch OFF-2. Disconnect the negative bat-tery cable from the battery.3. Disconnect the ECM connector C (31P).
4. Disconnect the ALT GRN 4P(3Pi* connector from the ALT.5. Connect the ALT GRN 4P (3p)*
connector terminal No. 4 (No.'l)* to body ground with a
6. Check for continuity betweenbody ground and ECM connector terminal C17.
Ropair open wire bstw€an theECM {C17} and rhe ALT.ls there continuity?
ri Canada
11-101

Starter Switch Signal
This signals the ECM when the engine is cranking.
NOTEI. M/T:Clutch pedal must be depressed.. A,/T: Transmission in E or E position.
Wire sida of female terminals
Check for an opon or short in thcwi.. ISTS lin.l:Measure voltage between ECMconnector terminals C6 and Agwith the ignition switch in thostart position (lll).
Inspect the No.31 STARTER SIG-NAL (7.5 Alluse in the under-dashfuse/relay box,
ls there battery voltage?
- Repair 3hort in the wire be-tween tho ECM lc6l rnd theNo. 31 STARTER SIGNAL (7.sAl tus€ or the PGM-FI mainr€lay.- Roplace the No. 31 STARTERSIGNAL 17.5 Al fuso.
Starter switch signal b OK.
Ropair open in tho wire botwaonih6 ECM {CGl and the No, 3lSTARTER SIGNAL {7.5 Al fuse.
11-105

{From page 11-'106)
Check tor an op€n in the wiro {ATpPN lin€):Turn the ignition switch OFF.Fgconnect the 10P connectorto the gauge assembly.Reconnect the 26P connectorto the TCM.stan the engine.M€asure voltage between ECMconnector termanals C29 andAg with the transmission inE position.
- Ropair open in th6 wiro bo-twoen tho ECM {C291 and thogru96 a3sgmbly.- Repair open in GRN wir. bo-twaan thc gauga !srembly.nd tho A/T g.ar po3itiongwitch.
ls there less than 1.0 V?
Chod( for an opon in tho wir6 (ATPPN linel:Measure voltage between ECMconnector terminals C29 and A9with the transmission in E] posi,tron.
R.psir op.n in GRN/WHT wirob€twcan th. gaugc rsr.mbly andthc A/T ge.r po.ition 3whch.
ls there less than 1.0 V?
A/T g6er position signal i3 OK.
a l32P)LGl{BRN/BLKI
Wire side of female terminals
ATP PN{I-T GRN/BLKI
11-107