1998 HONDA CIVIC cool

PGM-FI System
t
I
Engine Coolant Temperature (ECT) Sensor
('99 - 00 Models except Dl6Y5 engine with M/Tl
The scan tool indicates Diagnostic Trouble Code (DTC) P0118: A high voltage (low temperature) problem in the
Engine Coolant Temperature (ECT) sensor circuit.
ECT SENSOR 2P CONNECTOR {C122)
ECT(RED/Wr{T)
JUMPER IVIRE
sG2{GRN/BLK)
wire side of female terminals
ECM/PCM CONNECTOB C 131PI
The MIL has been reported on,
oTC P0118 is stored.
Problem verilication:1. Turn the ignition switch ON (ll).
2. Check the ECT with the scan
tool.
lntormittent failuro, systom is OK
at thb timo. Check lor poor con'nections or 10036 wiraa at C122
{ECT ssnsorl and ECM/rcM.
ls -4'F (-20"C) or less lor L-Limit
in Honda mode o{ PGM Tester) or
5 V indicated?
Check for an open in the Efi sen'
sori1. Disconnect the ECT sensor 2P
connector,2. Connect the ECT sensor 2P
connector terminals No, 1 andNo. 2 with a jumper wire.3. Check the ECT with the scantool.
ls -4"F 1-20"C) or less (or L-Limit
in Honda mode of PGM Tester) or
5 V indicated?
Check for sn open in the wires
IECT. SG2 linesl:1. Turn the ignition switch OFF.2. Connect ECM/PCM connectorterminals C18 and C26 with ajumper wire.3. Turn the ignition switch ON (ll).
4. Check the ECT with lhe scantooi.
Rspair opon in th6 wiros bstwoon
ECM/PCM (Cl8, C26l and ECT
3ensot.
ls -4'F {-20"C) or less (or L-Limit
in Honda mode of PGN4 Tester) or
5 V indicated?
Substitute 6 known-good ECM/PCM and recheck. l{ no.mal EcT
is indicatod, .eplace the originalECM/PCM.
JUMPER WIRE
Wire side of female terminals
11-131

ldle Control System
System Description
The idle speed ot the engine is controlled by the ldle Air Control (lAC) Valve.The valve changes the amount of air bypassing into the intake manifold in response to electric current controlled bv theECM/PCM. When the IAC Valve is activated, the valve opens lo maintain the proper idle speed.
D16Y5, D16Y8, Br6A2 engine (M/T):
(ROTARYItac vat-vEEI{GINEcooLAI{T
VARIOUSsEI{SORS
VARIOUSSENSORS
INTAKE MANIFOTDDl6Ys {CVTl, D16Y8 engine lA/T):
D16Y7 engine:
{ROTABY)
;iy--, - --- INTAKEMANIFOLD
11-190

1.After the engine starts, the lAc valve opens for a certain time. The amount of air is increased to raise the idle speed
about 150 - 300 rpm.
When the coolant temperature is tow, 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'
IOLE SPEED
lrpml
176
80
ENGI ECOOLANI TEMPERATURE
t" Fl
toc)
ll
't.Whentheid|espeedisoutofspeciiicationandthescantoo|doesnotindicateDiagnosticTroub|ecode(DTc)P0505
or P1508. check the following items:
. Adiust the idle speed {see page 11-220}
. Starter switch signal (see page 11-202)
. Air conditioning signal (see page l1-204)
. ALT FR signal (see Page 11-2081
' Brake switch signal (see page 11-210)
. PSP switch signal (excapt Canada model) (see page 11-212)
. A,/T gear position signal {see section 14, Dl6Y5 engine (CVT):
page 11-216). Clutch switch signal (D16Y5 engine with M/T) (see page 11-218)
. Hoses and connections
' IAC valve and its mounting O-rings
lf the above items are normal, substitute a known-good IAC valve and readjust the idle speed (see page 11-220)
|ftheid|espeedsti||cannotbeadjustedtospecification(andthescantoo|doesnotindicateDTcP0505orP]50S)
after IAC valve replacement. substitute a known-good ECM/PCM and recheck. lf symptom goes away, replace the
original ECM/PCM.

ldle Control System
ldle ControlSystem
lF0505 l Th" """n tool indicates Diagnostic Trouble Code (DTC) PO5O5: tdte controt system malfunction.
NOTE: lf DTC P1508 or P1509 is stored at the same time as DTC P0505, troubleshoot DTC p1508 or p1bog first. thenrecheck for DTC P0505.
Possible Cause
. IAC valve mechanical malfunction
. Throttle body clogged pon, improper adjustment. Intake manifold gasket leakage
. Intake air hose loose leakage
. Vacu um leak
. ECT sensor incorrect output
. Throttle Position sensor incorrect output*r
Troubleshooting Flowchart
The MIL has been reoorted on.DTC P0505 is stored.
Problem verification:1. Start the engine. Hold theeng;ne at 3,000 rpm with noload (jn Park or neutral) untilthe radiator fan comes on, then*r let it idle.t2. with rhe scan toot, ct'eit Ge l
Throttle position should beapprox. 10% with the throttle fully closed.E ngine coolant tempera-ture should be 194 205'F(90 96.Ci.lf they are not within thespec., repair the faulty sen
L._ _9oI9[cr]41 l3. Chec& the engine speed atidle with no-load cond;tionsiheadlights, blower fan, reardefogger, radiator fan, and airconditioner are not operating\see page l1-22O - 223).
Intermittent tailure, system is OKat this time.ls the idle speed OK?
ls it 550 rpm or less?
(To page 11,193)
*1r'96 models only
11-192
(To page ll-193)

ldle Gontrol System
Air Gonditioning Signal ('96 - 98 Models, '99 - 00 Dl6Y5 engine with M/Tl
a {32P1ECM/PCM CONNECTORS
Wire side of female terminals
c l3lPl
This sjgnals the ECM/PCM when there is a demand for cooling from the air conditioning system.
(To page 11-205)
Check for a short in the wire{ACS line):1. Turn the ignition switch OFF.2. Disconnect the A/C pressure
switch 2P connector {see section 22).3. Turn the ignition switch ON (ll).
4. Measure vo lta ge betweenECM/PCM connector termi-nals C5 and A9.
Check for a .hort in the wi.e {ACSline):1. Turn the ignition switch OFF.2. Disconnect the ECM/PCM con-nector C (3lPi.
3. Check tor continuity betweenbody ground and ECM/PCMconnector terminal C5,
ls there approx. 5 V?
Reotir short in the wi.e betweenthe ECM/PCM lc5l and rhe A/Cpressure switch.
ls there continuity?
- Substitute a known-goodECM/rcM .nd re.fieck. f Dre-scribed voltage is now availtble, replace the original ECft4/PCM,- See the air conditioner inspe-tion ls€e s€ction 221.
Check tor an op€n in the wireIACC lin6l:1. Turn the ignition switch OFF.2. Reconnect the A/C pressure
switch 2P connector.3. Turn the ignition switch ON (ll).
4. Momentarily connect ECM/PCM connector terminals A9and A17 with a jumper wire
LGl IBRN/8LKIACS {BLU/RED)
2361I9't0Itt3a89t0
12't31al5l617t8t920232all12l3l!ai5!617'tE
252l2A2930232a252930
ACS (BLU/BEDI
LGl IBRN/BLKI
123aslslrl lolgl ro lrr I
121314l516y)nltslnl/@) zr I zr I
25271!M1 1-/r
ACC
11-204
IBLK/RED)JUMPER WIRE

ldle Control System
Air Conditioning Signal ('99 - 00 Models except Dl6Y5 engine with M/Tl
This signals the ECM/PCM when there is a demand for cooling from the air conditioning system.
ECM/PCM CONNECTORS
a l32P)
ECM/PCM CONNECTOR A {32P)
Wire side of female terminals
ECM/PCM CONNECTORS
A (32P1
Chock tor a short in ihe wi.e(ACS lin6):1. Turn the ignition switch OFF.2. Disconnect the A/C pressure
switch 2P connector.3. Turn the ignition switch ON (ll).
4. Measure vo ltage betweenECM/PCM connector terminals A27 and 820.
Check for a short in the wire (ACS
linel:'1. Turn the ignition switch OFF.2. Disconnect the ECM/PCM connector A (32P).
3. Check lor continuity betweenbody ground and ECM/PCMconnector terminal A27.
Reoair short in lhe wi.e botweonthe ECM/PCM (A271 and rhe A/Cpressure swilch.
Srr66tituto a known{ood ECM/PCt4 tnd rechock. It prascrib€dvoltage is now available, re-plac€ the original ECM/rcM.Soo the air conditioner insoec-tion {see s€ction 22}.
Check to. an opon in tho wi.e(ACC linel:1. Turn the ignition switch OFF.2. Reconnect the A/C pressure
switch 2P conneclor.3. Turn the ignition switch ON (ll).
4. Momentarily connect ECN4/PCM connector terminals A17and 820 with a jumper wire
(To page '! 1-207)
11-206
LGl {BRN/BLK)

Intake Air System
\JSystem DescriPtion
The system supp|ies air for a|| engine needs' |t consists of the intake air pipe' Air C|eaner (ACL}, intake air duct, Thrott|e
Body (TB), ldle Air control (lAc) valve and intake manifold. A resonator in the intake air pipe provides additional silencing
as air is drawn into the system.
D16Y5, D16Y8, 816A2 engine {M/Tl
YEL/ - From PGM-FIaLK - MA|N RELAY
BLK/BLU
-- ORN
INTAKEAIRDUCT
IROTARYIIAC VALVE
Iaru
ENGINECOOLANT
BLK/
INTAKEAIR DUCT
I
D16Y5 engine (CVT), D16Y8 engine (A/T)' f'ttlxr ,tla"tpoto
D16Y7 engine:
{ROTARY)IAC VALVE
VARIOUSSENSORS
INTAKEAIRPIPE
tr
RESONATOR
!r,
IAC VALVE
BLK
11-243

IThrottle BodY
Description
The throttle bodY is either a single-barrel side-draft type
(D16Y5, D16Y8, 816A2 engine) or a down-draft type
(D16Y/ engine). The lower portion ot the throttle valve is
heated by engine coolant from the cylinder head' The
idle adjusting screw which regulates the bypass air is
located on the top of the throttle body
THROTTLEPOS|T|ON lTPlSENSOR
IDLE AD.'USTINGSCREW
t
In3pection
1. Check that the throttle cable operates smoothly
without binding or sticking.
lf there are any abnormalities, check for:
. Excessive wear or play in the throttle valve shaft'
. StickY or binding throttle lever at the fully closed
Position.. Clearance between throttle stop screw and throt-
tle lever at the fully closed position'
D16Y5, Dl6Y8 engine:
THROTTLE STOP SCREW
{Do not adjust.)
Dl6Y7 ongine:
816A2 engins:
THROTTLE LINK
STOP SCREW
THROTTTE STOP SCREW(Do not adjust.)
Replace the throftle body if thsre is excessive play in the
throttle valve shaft or iJ the shaft is binding or sticking'
(cont'd)
11-247
{Do not adjust.)