1998 ACURA INTEGRA intake

3.Fuel Cut-off Control
. Du ring dece leration with the th rottle va lve closed, cu rrent to the fuel injectors is cutoffto improvefuel economyat
speeds over following rpm:. B'1881 engine: 970 rpm {Canada model: 1.050 rpm). B18C1 engine:970 rpm {Canada model: 1.050 rpm). 818C5 engine: 1,300 rpm (Canada model: 1,400 rpm)
. Fuel cut-off action also takes place when engine speed exceeds 7,000 rpm (B'1881 engine), 8.100 rpm (818C1
engine) or 8,600 rpm (818C5 engine), regardless ol the position of the thronle valve, to protect the engine from
over-revving.
A,,/C ComDressor Clutch Relav
When the ECM receives a demand for cooling from the air conditioning system, it delays the compressor from being
energized, and enriches the mixture to assure smooth transition to the A,/C mode.
Evaporative Emission (EVAP) Purge Control Solenoid Valve
When the engine coolanl temperature is above '154'F (68'C) and the air conditioner on. the ECM controls the EVAPpurge control solenoid valve which controls vacuum to the EVAP purge control canister.
Intake Air Eypass (lAB) Control Solenoid Valve*a
When the engine rpm is below 5,750 rpm, rhe IAB control solenoid valve is activated by a signal from the ECM, intake
air flows through the long intake path, then high torque is delivered. At speeds higher than 5,750 rpm, the solenoidvalve is deactivated by the ECM, and intake air flows through the short intake path in order to reduce the resistance in
airflow.
Sell-diagnosis Function lMalfunction Indicator Lamp {MlL)lWhen an abnormality occurs in a signal from a sensor, the ECM supplies ground for the MIL and stores the code in
erasable memory. When the ignition is initially turned on, the ECM supplies ground for the N4lL tor two seconds to
check the MIL bulb condition.
Two Driving Cycle Detection Method
To prevent false indications, the Two Driving Cycle Detection Method is used for the HO2S, fuel metering-related, idle
control system, ECT sensor, TWC and EVAP control system and other self-diagnostic functions, When an abnormality
occurs, the ECM stores it in its memory. When the same abnormality recurs after the ignition switch is turned OFFand ON (ll)again, the ECM informs the driver by lighting the MlL.
However, to ease troubleshooting, this function is cancelled when you shon the service check connector. The MIL will
then blink immediately when an abnormality occurs.
4.
5.
6.
3.
4.
ECM Fail-safe/8ack.up F0nctions
1. Fail-sate Function
When an abnormality occurs in a signal from a sensor, the ECM ignores that signal and assumes a pre-programmed
value for that sensor that allows the enqine to continue to run.
2. Back-uo Function
When an abnormality occurs in the ECM itself, the fuel injectors are controlled by a back-up circuit independent of the
system in order to permit minimal driving.
11-49

PGM-FI System
Intake Air Temperatute (lATl Sensor
The scan tool indicates Diagnostic Trouble Code (DTC) P0112: A low voltage (high temperature) problem in the
lntake Air Temperature (lAT) sensor circuit.
The IAT Sensor is a temperature dependant resistor (thermistor). The resistance of the thermistor decreases as the intake
air temperature increases as shown below.
RESISTANCE IKO)
THERMISTOR
l1\
\'/
rb lllo,'.u
I
1r3 2r2 2.a l.Flm roo r20 toc)
INTAKE AIR TEMPERATURE
lf the engine is warm, it will be higherthan ambient temperature.
IAT SENSOR CONNECTOR ICl2OI
- The MIL h.s b€an rooorted on.- DTC P0112 is stored.- Or lrom Probable Cau3e List.
P.oblem v6rificationi1. Turn the ignition switch ON lll).2. Check the IAT wirh the scantool.
ls 302'F (150"C) or higher (or
H Limit in Honda mode o{ thePGM Tester) or 0 V indicated?
ls the correct ambient temPerature indicated*?Roolace the IAT sensor.
Into.mittent feilur6, aystem h OKat this timc. Check to. Doot con-nections or loose wires at Cl20{lAT sensor) snd ECM.
Check tor a 3hort in the IAT sen-
1. Disconnect the IAT sensor con
2. Check the IAT with the scantool.
ls 302"F (150'C) or higher (or
H Limit in Honda mode of thePGM Tester) or 0 V indicated?Reolace the IAT sonsor.
Check for a short in the wire (lAT
line):1. Turn the ignition switch OFF.2. Disconnect the ECM connec-tor D (16P).
3. Check for continuity betweenIAT sensor connector terminalNo.2 and body ground.
Rooair short in the wirc botwoenECM {D8) .nd IAT sen3or.ls there continuity?
Substitut€ s known-good ECMand rccheck. lI normal IAT is indi-cated, replace the originel ECM.
1 1-58
Wire side of lemale terminals
L

The scan tool indicates Diagnostic Trouble Code (DTC) P0113: A high voltage (low temperature) problem in the
Intake Air Temperature (lAT) sensor circuit.
IAT SENSOR CONNECTOR ICl2OI
sG2IGRN/BIKI
JUMPEB WIRE
IAT IREDTYELI
Wire side of temale terminals
ECM CONNECTOR D (t6PI
IAT
sG2IGRN/BLUI
tRED/YEL)-JUtvtPERWTRE
Wire side of female terminals
Tho MIL ha3 b€on i6ponod on.DTC m113 i3 3lor.d.
Problom vcrification:1. Turn the ignition switch ON (ll).
2. Check the IAT with the scantool.
Int.rmitt.nt t.ilura. .yatrm iaOK .t thi! tim.. Ch.ck fo. poolconnaclion3 or loota wirca atC120 llAT r.nrorl .nd ECM.
ls -4"F {-20"C}or less (or L-Limit in Hond mode of PGMTester) or 5V indicated?
Ch.ck tor an open in ihe IAT s6n-30r:1. Disconnect the IAT sensorconnectot,2. Install a jumper wire betweenthe two terminals on the IATsensor connector,3. Check the intake air tempera-ture with the scan tool.
ls -4'F (-20"C) or less {or L-Limit in Hond mode of PGMTester) or 5 V indicated?
Chock to. an opon in thc wiros(lAT, SG2 lin6l:1. Turn the ignition switch OFF.2. Install a jumper wire betweenECM connector terminals D8and D11.3. Turn the ignition switch ON lll).4. Check the IAT with the scantool.
ls -4'F {-20'C} or less (or L-Limit in Hond mode ot PGMTester) or 5 V indicated?
Raprir opan in tha wira!b.tw.cn ECM {D8, D11} and th.lAT aanao.,
Subatitut6 a known.good ECM.nd roch.ck. ll normal IAT i. indi-cated, roplacc the o.iginal ECM.
1 1-59

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

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

ldle Control System
Fast ldle Thermo Valve (A/T model onlylFast ldle I nermo valve (A/ | mooel
Description
To prevent erratic running when the engine is warming
up. it is necessary to raise the idle speed. The fast idle
thermo valve is controlled by a thermowax plunger.
When the engine is cold, the engine coolant surround-
ing the thermowax contracts the plunger, allowing addi
tional air to be bvoassed into the intake manifold so that
the engine idles taster. When the engine reaches operat-
ing temperature, the valve closes. reducing the amount
of air bypassing into the manifold.
FAST IDLE THERMO
VALVE
VALVE
wAx
Inspection
NOTE: The fast idle thermo valve is factory adiusted; it
should not be disassembled.
1. Remove the intake air duct from the throttle body.
2. Start the engine.
3. Put your finger over the lower port in throttle body
and make sure that there is air flow with the engine
cold {engine coolant temperature below 86'F, 30"c).
LOWERPORT
lf there is no air flow, replace the last idle thermo
valve and retest.
Start the engine. Hold the engine at 3,000 rpm with
no load (in Park or neutral) until the radiator fan
comes on, then let it idle.
Check that valve is completely closed. lf not, air suc-
tion can be felt at the lower port in the throttle body.
l{ any suction is felt, the valve is leaking. Check
engine coolant level and for air in the engine
coolant system (see section 10). It OK, replace the
fast idle thermo valve and recheck.
5.
{1.0 kg.m,7.2lbftl
l
11-110
lL.