1996 HONDA CIVIC o2 sensor

\
lTo420l Th" """n toot indicates Diagnostic Troubte code (DTc) p0420: catatyst sysrem efficiency below threshold.
Description
This system evaluates the catalyst's capacity by means of the Ho2s {Primary and secondary) output during stable driving
conditions. ll deterioration has been detected during two consecutive driving cycles. the MIL comes on and DTC P0420 will
be stored.
NOTE: lf some of the DTCS tisted below are stored at the same time as DTC P0420, troubleshoot those DTCS first. then
recheck for DTC P0420
P0137, P0138: Secondary HO2S (Sensor 2)
Po14'1:Secondary H02S {Sensor 2) Heater
Possibl€ Cause
. TWC Deterioration
. Exhaust system leakage
Troubleshooting Flowchart
I
The MIL has been reported on.
DTC P0420 is stored
Problem verilication:1. Do the ECM/PCM Reset Proce
dure.2. Start the engine Hold the
engine at 3,000 rpm wath no
load {in Park or neutral) until
the radiator fan comes on.
3. Connect the SCS service con
4. Test drive 40 - 55 mph for
approx, two minutes Then
decelerate for at least 3 sec_
onds with the throttle com'pletely closed- Then reduce
the vehicle speed to 35 mph,
and try to hold it until the
readiness code comes on
Intermittent Iailure, system is OK
at this time.ls DTC P0420 indicated?
Check the TWC {see section 9l
lf necessary, replace the TwC

Emission Control System
Exhaust Gas Recirculation (EGR) System (D16yS engine)
Doscription
The EGR system is designed to reduce oxides of nitrogen emissions (NOx) by recirculating exhaust gas through the EGRvalve and the intake manifold into the combustion chambers. lt is composed of the EGR valve. EGR vacuum conrrot vatve.EGR control solenoid valve. ECM and various sensors.The EcM contains memories for ideal EGR valve lifts for varying operating conditions, The EGR valve lift sensor detectsthe amount of EGR valve lift and sends the information to the ECM. The ECM then compares it with the ideat EGR valve liftwhich is determined by signals sent from the other sensors. lf there is any difference between the two. the EcM cuts cur-rent to the EGR control solenoid valve to reduce vacuum applied to the EGR valve.
EGR CONTROLCVT: SOLENoID vALvE
EGN VALVE LIFT SENSOR
BLK
I
I
11-254

Emission Control System
Exhaust Gas Recirculation (EGR) System (D16Y5 engine with GWI (cont'dl
lTl49il T_he scan tool indicates Diagnostic Trouble Code (OTC) P1491: A malfunction in the Exhaust Gas Recirculation- lEgh) svstem.
CvT lM/T see page 1l-2611:
J
EGR VALVELIFT SENSOR#16 HOSE
PUMP/GAUGE,0- 30 in.HsA973X-041-XXXXX
EGRVALVE
The MIL has been reoorted on.DTC P1491 is stoled.
Problem verification:1. Do the ECM/PCM Reset Proce-du re.2. Connect the SCS service con'
3. Start the engine. Hold theengine at 3,000 rpm with noload {in Park or neutral) untilthe radiator fan comes on,4. Drive the vehicle on the roadfor approx. 10 minutes. Try tokeep the engine speed in the1,700 - 2,500 rpm range.
Intermittonl failure, system is OKat this time. Check for Door con-nections or loose wires at, C144{EGR velve} and ECM/PCM.
ls DTC P l49l indicated?
Check fo. vacuum to ihe EGR
1. Disconnect the No. 16 hose fromthe EGR valve.2. Connect a vacuum pump/gauge to the hose.3. Start the engine and let it idle.
ls there any vacuum?
Check tor a malfunction in theEGR control solenoid valve:'1. Disconnect the EGR controlsolenoid valve 2P connector,2. Becheck the No. 16 hose for
Check vacuum hose routing o,the entire EGR svstem. lf hoserouting is OK, replac€ the EGRcontrol solenoidvalv6.
ls there any vacuum?
Substitute a known-good ECM/PCM and recheck. It symptom/indicalion goes away, replacethe original ECM/PCM.
(To page 11 257)
11-256

\EGR VALVELIFT SENSOR#16 HOSE
I
(From page 11-256)
EGR VALVE LIFT SENSOR3P CONNECTOR lC14.l)
zF vcczI- . ] IYEL/BLU)ll 2l3l---l-r_ 7 |
v-,, ISG2IGRN/BLK) I ^ II{Vts
ECM CONNECTOR D {16P)
PUMP/GAUGE,0 - 30 in.Hs4973X-041-XXXXX
sG2(GRN/BLKIvcc2IYEL/BLU}
Wire side ol temale terminals
PCM CONNECTORS C (31P}'
YES
Wire side of female terminals
1
(cont'd)
1-257
Check fo. a mallunction in theEGF valv€:1. ldove the vacuum pump/gauge
to the EGR valve.2. With the engine at idle, apply
26.7 kPa (200 mmHg,8.0 in.Hg)
ofvacuum to the EGR valve.
Does the engine stall or runrough and does the EGR valvehold vacuum?
Check for an open in the wire
IVCC2linel:1. Turn the ignition switch OFF.2. Disconnect the EGR valve liftsensor 3P connector.3. Turn the ignition switch ON (ll).
4. Measure voltage between theEGR valve lift sensor 3P con'
nector terminals No. 3 and
No.2.
ls lhere approx.5 V?
Check for an oDen in the wire
{VCC2 line}:Measure voltage between theECM/PCM connector terminalsD10 and Dl1 (C18 and C28)*.
Rep.ir open in the wire betweenrhe EGR valve snd ECM/PCM
{Dl0 {C28)*).lsthere approx.5 V?
Sub3titute t known-good ECM/PCM end recheck. lt 3ymptom/indication goos eway, replaceth6 original ECM/PCM.(To page 1l-258)*: '99 - 00 models

Emission Gontrol System
Exhaust Gas Recirculation (EGRI System (Dl6Y5 engine with CW) (cont'dl
EGR VALVE LIFT SENSOR3P CONNECTOR {Cl251
./
EGR L(WHT/BLKI
EGR LIWHT/BLKI
EGR L{WHT/BLKI
sG2
{GRN/BLK}
sG2{GRN/BLK}
Terminal side ol male terminal
ECIT'I CONNECTOR D II6PI
Wir€ side of f€male terminals
PCM CONNECTORS C (31PI*
{To page 11-259)
11-258
{From page 11-257}
Chock lor an opcn or short in th.EGR v.lve lift .€nsor'1. Turn the ignition switch OFF.2. At the sensor sid€, measur€resistance between the EGRvalve lift sensor 3P connectorterminals No. 1 and No.2.
ls there continuity or resis'tance ot 100 k0 or higher?
Chock tor sn op€n or lhort in theEGR valve lift lonror:Measure resistancg between theEGR valve lift s€nsor 3P connec-tor terminals No. 1 and No. 3.
ls there 100 k0 or higher?
Ch.ck tor an ooon or rhon in thcwiro IEGRL linc):1. Beconnect tho EGR v6lve liftsensor 3P connector.2. Turn tho ignition switch ON (ll).
3. Measure voltage between theECM/PCM connector terminalsD9 and Dl1 (C6 and C18l*.
ls there approx. 1.2 V?
(To page 11-259)
Wire side of female terminals

Emission Control System
(From page 11-261)
Check tor open in the wire (SG2
linel:Measure voltage between theECM connector terminals D10and D11.
Repsir open in lhe wire beiweenECM lOllland EGR valve.ls there approx. 5 V?
Check the EGR valve:1. Turn the ignition switch OFF.2, At the sensor side, measureresistance between the EGRvalve 6P connector terminalsNo. 1 and No. 2.
ls there continuity or resis-tance of 100 k0 or higher?
Check the EGR valve:Measure resistance between theEGR valve 6P connector terminals No. 1 and No.3.
ls there 100 k0 or higher?
Exhaust Gas Recirculation System (D16Y5 engine with M/T) (cont'dl
ECM CONNECTOR D {16P)
vcc2(YEL/BLU)
\v
sG2IGRN/BLK)
Wire side of female term;nals
EGR VALVE 6P CONNECTOR
EGR L(WHT/
BLK}
SG2 (GRN/BLK)
Termanal side of male terminals'l'
EGR L{WHT/BLK}
vcc2
{YEL/BLU}
(To pase 11 263)
1-262

J\
Exhaust Gas Recirculation System
The scan tool indicates Diagnostic Trouble
Recirculation (EGRlvalve lift sensor circuit.
(D16Y5 enginel
Code {DTC) P1498: A high voltage problem in the Exhaust Gas
EGR VALVE LlFf SENSOR 3P {M/T: 6Pl CONNECTOR (C1441
cvT:
vcc2{YEL/BLUI
SG2 IGRN/BLK)
IM/T:sG2{GRN/BLKI
Wir€ side ol lemale terminals
ECM CONNECTOR D (16P)
vcc2(YEL/BLUIsG2(GRN/BLK)
Wir€ side of female terminals
PCM CONNECTORS C 131P)'
Wire side oI female terminals
11-265
- The MIL has been reportod on.- DTC P1498 is storod.
Probl€m verification:1. Do the ECM/PCM Reset Proce
dure.2. Stan the engine.
Intermittent tailure, sy3lem is OK
at lhis time. Check tor poor con'
nections or loose wire3 at C144
|EGR valvel and ECM/PCM.
ls DTC P1498 indicated?
Check for an open in tho EGRvalv6 lift sen3or:1. Turn the ignition switch OFF.
2. Disconnect the EGR valve lift
sensor 3P (M/T: 6Pl connector.
3. Turn the ignition switch ON (ll).
4. Measure voltage between the
EGR valve litt sensor 3P lM/T:6P) connector terminals No. 3and No.2.
ls there approx.5 V?
Check lor op€n in th€ wire (SG2
line):Measure voltage between ECM/PCM connector terminals 010 andD1l (C18 and C28)*.
Repair open in tho wiro betwoen
ECM/PCM lDl1 (Cl8)r) and EGR
valvo lift sensor.ls there approx. 5 V?
Substitute . known-good ECM/PCM and recheck. ll symptom/indicrtion goes away, replacothe original ECM/rcM.
*:'99 - 00 D16Y5 engine with CVT

Emission Control System
Evaporative Emission IEVAPI Controls (cont'd)
'96 D16Y8 ongins (coupol.'97 D16Y8 €ngino (coups: all mod€ls, sedan: KL model),'98 D16Y5 engine (all mod6lsl,'98
Dl5YB engine {all modols):
{BLK/YEL
From
< No. 15
FUELTANKPRESSURESENSOR
EVAP PURG€CONTROLSOLENOID VALVE
. LT GRN
GRN/BLK
ALTERNATORSP SENSOR(7.5 A)
VARIOUSSENSORS
YEL/BLU
V€NT SHUT
EVAPBYPASSSOLENOIDVALVEL BLU
WHTRED/YEL
L __ LT GRN/
EVAPTWO WAYVALVE
INTAKEMANIFOI.I'
'97 D16Y7 engin. (coupa: KL model, sedan: KL {LX) model},38 Dl6
/ engine:
?:y- -<
FromNo. 15ALTERNATORSP SENSOR17.5 A)
FUELTANKPRESSURESENSOR
YEL/BLULT G]GRN/BLK
LT GRN/WHT
BLU
YEL
EVAPBYPASSRED/
VALVE
EVAPTWO WAVALVE
EVAP CONTROLCANISTER
FUEL FILLCAP
BLK
11-268
FUEL TANK