idle control HONDA CR-V 1998 RD1-RD3 / 1.G User Guide

Troubleshooting
Troubleshooting Procedures (cont'd)
DataDescliptionOperating ValueFreezo Data
HO2S
Feedback
Loop Status
Loop status is indicated as "open" or "closed".
Closed: Based on the HO2S output, the ECM/pCM deter-mines the airlfuel ratio and controls the amount ofinjected fuel.
Open: ignoring HO2S output, the ECM/pCiM refers to sig,nals from the TP, MAP, and ECT sensors to control theamount of injected fuel.
At idle speed: closed
YES
Short Term
Fuel Trim
The airlfuel ratio correction coefficient for correcting theamount of injected fuel when HO2S feedback is in theclosed loop status. When the signal from the HO2S isweak, short term fuel trim gets higher, and the ECM/PCMincreases the amount of injected fuel. The airlfuel ratiogradually gets richer, causing a higher HO2S output.Consequently. the short term fuel trim is lowered. andthe ECM/PCM reduces the amount of injected fuel.This cycle keeps the airfuel ratio close to the stoichio-metric ratio when in closed looD status.
t:20y"
YES
Long Term
Fuel Trim
Long term fuel trim is computed from shon term fueltrim and indicates changes occuring in the fuel supplysystem over a long period.
lf long term fuel trim is higher than 1,00. the amount ofinjected fuel must be increased. lf it is lower than L00.the amount of injected fuel must be reduced.
! 20%
Intake Air
Temperature
(IAT)
The IAT sensor converts intake air temperature into volt-age and signals the ECrU/PCM. When intake air tempera-ture is low, the internal resistance of the sensorincreases, and the voltage signal is higher.
With cold engine:
Same as ambient temper-
ature and ECTYES
Throttle
Position
Based on the accelerator pedal position, the openingangle of the throttle valve is indicateo.At idle speed:
approx. 10%
lgnition
Timing
lgnition timing is the ignition advance angle set by theECM/PCM. The ECM/PCM matches ignition timing to thedriving conditions.
At idle speed: 16'1 4.
BTDC with the SCS ser-
vtce connector connected.
NO
Calculated
Load Value(cLV)
CLV is the engine load calculated from the MAp data.At idle speed:
2A - 410/o
At 2,500 rpm with no load:
13 - 260/o
YES
_
1 1_66
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Powertrain Control Module Terminal Arrangement -'97 Model
FCM CONNECTOR A (32P)NOTE: Standard battery voltage is 12 V.
Wire side of lemale terminals
f€rminalnumlreJWirecolor
Telminalnama
DescriptionSignal
YELlNJ4 (No.4 FUELINJECTOR)Drives No. 4 {uel injector.With engine running: duty controlled
2BLUlNJ3 (No.3 FUELINJECTOR)Drives No. 3luel injector.
REDlNJ2 {No.2 FUELINJECTOR)Drives No.2 tuel injector.
BRNlNJl (No. l FUELINJECTOR)Drives No. 1 fuel injector.
5BLK WHTSO2SHIC (SECONDARY
HEATED OXYGEN SENSOR HEATER CONTROL)
D ves secondary heated oxygensensor heater.With ignition switch ON {ll): battery voltageWith fully warmed up engino running: dutycontrolled
6BLKAr'YHT
PO2SHTC (PRIMARY
HEATED OXYGENSENSOR HEATERCONTROL}
Drives primary heated oxygensensor heater,With ignition switch ON lll): battery voltagewith fully warmed up engine running: dutycontroll6d
I8RN/BLKLGl (LOGIC GROUND}Ground forthe PCM control circuit.Less than 1.0 V at all times
10BLKPG1 lPOWER GROUND}Ground for the PCM power circuit.
l1YEUELKIGPl lPOWER SOURCE}Power source for the PCM controlcircuit.
With ignition switch ON (ll): battery voltageWith ignition switch OFF: 0 V
12BLI(BLUIACV {IDLE AIRCONTROL VALVE}Drives IACV.With €ngine running: duty controlled
REDryEL
PCS (EVAP PURGECONTFOL SOLENOIDVALVE)
Drives EVAP purge controlsolenoid valve.
With engine running, engine coolantbelow 154'F (68"C): battery voltageWith engine running, engine coolantabove 154"F (68"C): duty controlled
16GRN/VELFLR (FUEL PUMP RELAY)Drives Iuel pump relay.0 V for two seconds after turning ignition
switch ON lll), then battery voltage
118LI(REDACC (A,/C CLUTCHRELAY}Drives Ay'C clutch relay.With comoressor ON: 0 VWith compressor OFF: baftery voltage
18GRN/ORNMIL (MALFUNCTION
INDICATOR LAMP}Drives MlL.With MIL turned ON: 0 VWith MIL turned OFF: baftery voltage
19*WHT/GRNALTC (ALTERNATOR
CONTROL}Sends alternator control signal.With tully warmed-up engine running:
battery voltageDuring driving with smallelectrical load:0 '
20YEUGRNICM (IGNITION CONTROLMODULE)Sends ignition pulse.With ignition switch ON (ll): baftery voltageWith engine running: pulses
22BRN/BLKLG2 (LOGIC GROUND}Ground tor the PCM control circuit.Less than 1.0 V at alltimes
23BLKPG2 {POWER GROUND}Ground lor the PCM power circuit.
24YEUBLKIGP2 {POWER SOURCE}Power source for the PCM controlcircuit.
With ignition switch ON (ll): battery voltage
With engine switch OFF: 0 V
27GRNFANC (RADIATOR FANCONTROL)Drives radiator {an relay.With radiator fan running: 0 VWith radiator fan stopped: baftery voltage
*: USA
{cont'd)
11-67
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PCM CONNECTOR C (31PI
ferminalnumberWirecolorTerminalnameDoscriptionSignal
'tBLUiREDCKFP (CKF SENSOR PSIDE)Detects CKF sensor.With engine running: pulses
2BLUCKPP (CKP SENSOR PSIDE)Detects CKP sensor.With engine running: pulses
3GRNTDCP (TDC SENSOR PSIDE)Detects TDC sensor.With engine running: pulses
4YELCYPP (CYP SENSOR PSIDE)Detects cYP sensor.With engine running: pulses
5BLU,frEDACS (A/C SWTTCHSIGNAL)Detects A,/C switch signal.With AJC switch ON: 0 VWith A,/C switch OFF: battery voltage
BLU/ORNSTS (STARTER SWITCHSIGNAL)
Detects starter switch signal.With starter switch ON (lll): bafteryvoltageWith staner switch OFF: 0 V
7BRNSCS (SERVICE CHECKSIGNAL)
Detects service check connectorsignal (the signal causing a DTCindication)
With the connector connected: 0 V
With the connector disconnected: about
5 V or battery voltage
8LT BLUK-LINESends and receives scan toolsrgnal.With ignition switch ON (ll): pulses
10WHT/BLUVBUUP)
(VOLTAGE BACKPower source tor the PCMcontrol circuit. Power source for
the DTC memory
Battery voltage at all times
11WHT/REDCKFM (CKF SENSOR MSIDE)Ground for CKF sensor signal.
12WHTCKPM (CKP SENSOR I\4SIDE)Ground lor CKP sensor signal.
13REDTDCM (TDC SENSOR MSIDE}Ground for TDC sensor signal.
14BLKCYPM (CKP SENSOR MSIDE}Ground for CYP sensor signal.
16GRN
PSPSW (P/S PRESSUREswtTcH)Detects PSP switch signal.At idle with steering wheel in straightahead position:0 VAt idle with steering wheel at full lock:
battery voltage
17WHT/REDALTF (ALTERNATOR FRSIGNAL)
Detects alternator FR signal.With fully warmed up engine running:
0 V-battery voltage {depending onelectrical load)
18BLUA/VHTVSS (VEHICLE SPEEDSENSOR)Detects VSS signal.Wirh ignition switch ON (ll) and frontwheels rotating: cycles 0 V - 5 V or bat-tery voltage
Wire side of femaie terminalsPCM CONNECTOR C {31PINOTE: Standard battery voltage is 12 V.
(cont'd)
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Engine/Powertrain Control Module Terminal Arrangement - 38 - 00 Models
ECM/PCM CONNECTOR A (32P}
,/./5aIsca
,/ l,/t5ItsTs
n2ls!uCI
Wire side ot female terminalsECM/FCM CONNECTOR A {32P)NOTE: Standard baftery voltage is '12 V.
D93criptionSignal
3BLU2WBS {EVAP BYPASSSOLENOID VALVE)Drives EVAP bvoass solonoid valve.With ignirion switch ON {ll)r battery voltage
LT GRNMHTVSV {EVAP CONTROL CANISTEB VENT SHUT VALVE)D.ives EVAP controlcanisler vent shutWith ig^ition switch ON (ll): battery voltage
5',BLUCRS (CRUISE CONTROL SIG'NAL)Shift Oown signalinputfrcm cruise conWhen cruise control is used: pulses
6RED/YEL
PCS (EVAP PURGE CONTROLSOLENOID VALVE)Drives EVAP purge controlsolonoid valve.With engins running, engine coolant, below 154'F(68'C)r battery voltageWith engine running, engine coolant, above 154"F{6a'C}r duty conl.olled
8ELIOWHTSO2SHTC (SECONDARVHEATED OXYGEN SENSORHEATER CONTROL)
Drives sacondary heated oxygen sensorWith ignition switch ON (ll): banery voltageWith fully warmed up engine running: duty
10BRNSCS (SERVICE CHECX SIGNAL)Detects seNics check conneclor signal(he signalcausing a DTC indicatjon)with rhe lerminal connected:0 vWith the rerminaldisconnectedrabout 5 v or
l4'rGRN/8LKD4IND (D4INDICATOR)+3DIND (D INDICATORTIDrives D4*3. Dr'indicaior light.W,rh 04' , O" indrcator light turned O batter,
With D4*3, D*. indicator light turned OFFr0 V
16GRNI/ELFLR (FUEL PUMP RELAY)Drivss fusl pump relay.0 V for iwo seconds after ru'nin9 ign'lion swilchON lll), then banery voltage
17AL|(/REDACC (I/C CLUTCH RELAY}Drives l,/C clurch rclay.With compressor ONr0 VWith compressor OFF: battery voltage
18GRN/ORNMIL (MALFUNCTION INDICA.TOR LIGHT)Driv€s MlL.With MlLturned ON:0 VWith MIL turned OFF: battery voltage
19BLUNEP (ENGINE SPEED PULSE)Outputs engine spsed pulse.With sngine runnin9: pulses
20GRNFANC {RADIATOR FAN CONTROL)Drives r6diator fan rslay.With radaator fan running:0 VWith radaatorfan stopped: battery vollage
218LU/t/ELK-LINESends and receiv€s scan toolsignal.With ignition switch ON (ll): p'rlses
23WHT/REDSHO2S (SECONDARY HEATEDOXYGEN SENSOR. SENSOR 2iDetects secondary h€at€d oxygen sensorWith throttle fully opened from idle wilh fullywalmed up engine: above 0.6 Vwith rhrottle quickly closed: below 0-4 V
21BLU/WHTSTS (STARTER SWITCH SIG,NAL}Dotocts srarter switch signal.Whh staner switch ON (lll): batlery voltageWith srarter switch OFF: 0 V
26GBNPSPSW {P/S PsESSUFESWITCH SIGNAL)Detecrs PSP switch signal.At idle with steeing wh€el in stBighl ahead position: 0 VAt idls with nee ng wheel al full lockr banory voltage
2fBLU/BEOACS (Ir'C SWTCH SIGNAL}D€tects ly'C switch signal.With Ay'C switch ON:0 VWith l/C swil€h OFF: about 5 V
2A'\WHT/NEDSLU {INTERLOCK CONTROLUNIT)Orives interlock control unil.With ignilion switch ON (ll)and brake pedaldepressed: battery vohage
29LT GRNPTANK (FUEL TANK PRES'SURE SENSOR)Detocts fueltank pressure sensor signal.With agnition switch ON (ll) and fuel fill capopensd; about 2.5 v
GBN/FEDEL (ELD}Detects ELD signal.Wirh paaing rightstumed on at idle:about 2.5 - 3.5 VWith low beam headlights tumed on at idle:about 1.5-2.5V
GRN/WHTBKSW (BRAKE SWTTCH)Dst€cts brake switch signal.Wirh brake pedal released:0 VWith brake pedal depressed: battery vollage
13: '98 modsl
15: USA(cont'd)
11-71
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Troubleshooting
Engine/Powertrain Control Module Terminal Arrangement - '98 - 00 Models
(cont'd)
ECM/PCM CONNECTOR B {25PI
Wire side of female terminalsECM/PCM CONNECTOR B I25PI
*2t MlT*3: '98 model"4: '99 - 00 models
NOTE: Standard baftery voltage is l2
Ierminalnumb€tWire colorTerminsl nameDescriptionSignal
1YEUBLKIGPl (POWER SOURCE)Power source for the ECM/PClvlcontrol circuit.withagewith
ignition switch ON (ll): battery volt-
ignition switch OFF:0 V
BLKPG1 (POWER GROUND}Ground for the ECM/PClvl controlcircuit.Less than 1.0 V at all times
REDlNJ2 (No. 2 FUEL INJEC-roR)Drives No. 2 Iuel injector.With engine running: duty controlled
BLUlNJ3 1No. 3 FUEL INJEC-TOR)Drives No. 3Iuel jnjector.
YELlNJ4 {No.4 FUEL INJEC-TOR)Drives No. 4 fuel injector.
8*1WHTLS- (A"/T CLUTCH PRES.SURE CONTROL SOLE,NOID VALVE _ SIDE)
A,/T clutch pressure controlsolenoid valve power supplynegative terminal.
With ignition switch ON (ll): dutycontrolled
9YEUBLKIGP2 IPOWER SOURCE)Power source for the ECN,I/PCMcontrol circuit.With ignition switch ON (lll: bafteryvoltageWith ignition switch OFF:0 V
10BLKPG2 (POWER GROUND}Ground for the ECM/PCM controlcrrcurt.Less than '1.0 V at all times
' BRNlNJl (No. 1 FUEL INJECTOR)Drives No. l tuel injector.With engine running: duty controlled
YEUGRNrcM {rGNrTroN coN-TROL MODULE)Sends ignition pulse.With ignition switch ON (ll): batteryvoltageWith engine running: pulses
17*1REDLS+ (A,,IT CLUTCH PRESSURE CONTROL SOLE-NOID VALVE + SIDE)
A,/T clutch pressure controlsolenoid valve power supplypositive terminal
With ignition switch ON (ll): dutycontrolled
19*.PNK
ODIND (OVER-DRIVE
OFF INDICATOR}Drives OVER-DRIVE OFFindicator light.With OVER-DRIVE OFF indicator lightturned ON: 0 VWith OVER-DRIVE OFF indicator lightturned OFF: battery voltage
20BRN/BLKLG1 (LOGIC GROUND)Ground for the ECM/PCM controlcircuit.Less than 1.0 V at all times
WHT/BLUVBU (VOLTAGE BACKUP)Power source for the ECM/PCMcontrol circuit.Power source forthe DTC memory.
Battery voltage at all times
22BRN/BLKLG2 (LOGIC GROUND)Ground for the ECN4/PCM controlctrcutt,Less than 1.0 V at all times
23BLVBLUIACV {IDLE AIR CON.TROL VALVE)Drives IAC valve.With engine running: duty controlled
11-72
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ECM/PCM CONNECTOF C (31PI
Wire side o{ female terminal€ECM/PCM CONNECTOR C (31P)NOTE: Standard battery voltage is 12 V.
TermidalD.3criptionSignal
8LI(WHTPOzSHTC {PRIII4ABY HEATEDOXYGEN SENSOR HEATERCONTROL)
Drivss prim6ry h$ted oxygsn sensorWilh ignition switch ON (ll): baneryvoltsgeWith ftrllywarmsd up €ngine runnang: duty
2"WHT/GBNALTC (ALTERNATOR CON,TROL)Sonds alternalor control signsl.With fully wafmod up €ngine rnningr ban€ryvoltagoDu ng driving with small elsctrical lo6d: 0 v
3'1FED/8LUKS (KNOCK SENSOR)Dstects KS signal.With engine knockang: pulses
5WHT/REDALTF (ALTERNATOR FR SIG-NAL}Detects alternator FR signal.Wth fullywarmed up €ngine running:0 V-batteryvoltag€ {d€pending on slsctrical load)
1GRN,4trHTSG1 (SENSOR 680UND}Ground for l/tAP sensor.L€ss than 1.0 v 6t all times
8BLUCKPP (CKP SENSOF P SIDE)Dat€cls CKP s6nsor.With €ngin€ runningr puls€s
9CKPI.,I| {CKP SENSOF M SIDE)Ground for CKP s€nsor.
15PHO2S {PRIMARY HEATEDOXYGEN SENSOR, SENSOR 1)Detocts pfimary he6t6d oxygen ssnsor
{sonsor 1)signal.with ihfottls fully opened from idle with fully,
walm6d up engins: above 0.6 VWith throttlo quickly clossd: below 0.4 v
17RED/GRNMAP (MANIFOLD ABSOLUTEPRESSURE SENSOR)
D6tects MAP s€nsor sign6l.With ignition switch ON (ll):about 3 VAt idls: aboul 1.0 V {dspsnding on engine speed)
18GRN/BLKSG2 (SENSOB GNOUNDiLsss than 1.0 V at all tim€s
19YEUBEDVCCl {SENSOR VOLTAGE)Power soufce to MAP s€nsor.With ignition switch ON (ll): about 5 VWith ignition switch OFF:0 V
20GRNTDCP {TDC SENSOR P SIDE)Derecis TDC sensor.With engine funning: Pulses
2lREDTDCM ITDC SENSOR M SID€)Ground for TDC sensor.
22BLU/REDCKFP (CKF SENSOR PSIDE)Dstscts CKF s€nsor.With sngins running: pulsss
23BLU/WHTVSS (VEHICLE SPEED SEN-soR)Dstscrs vss signal.With ignition switch ON (ll)and front wheelsrotaringrcyclss 0 v- 6bout 5 V or ban€ry voltage
25RED//ELIAT (INTAKE AIR TEMPERA'TURE SENSOB)Detacts IAT sensor signal.With igniiion switch ON (ll): about 0.1 - 4.8 V(d€p€nding on iniate air t€mp€raturc)
26REO/WHTECT {ENCINE COOLANTTEMPERATURE SENSOR)oetscts ECT sensor signal.With ignition switch ON (ll): about 0.1 4.8 V
{doponding on 6ngin€ coolanl lemper6tu16)
27RED/BLKTPS (THROTTLE POSITIONSENSOR)Dotects TP sensor signrl.with rhrottls fully op€n: aboui 4.8 vwith throtrl6 fullyclosed: about 0.5 v
2AYEUBLUVCC2lSENSOR VOLTAG€}Provid€s s€nsor voltage.With ignilion switch ON (ll): about 5 VWhh ignition switch OFF: 0 V
29YELCYPP ICYP SENSO8 P SIDE)Dsrscts CYP sensor.With €ngins runningr pulsss
30BLKCYPM (CYP SENSOR M SIDE)Ground for CYP sansor.
31WHT/REDCKFM {CKF SENSOR M SIDE)6.ound lof CKF ssnsor signal.
11. AfT 13. '94 model'2:M/T 14:'99- 0o modsls.5: USA
(cont'd)
11-73
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DTC(MlL indicationlDotection ltomProbable CausePage
P0500 t17)*,
Vehicle SpeedSensor CircuitMalfunction
Vehicle Speed SensorVehicle Speed Sensor circu itECtVI1 1-135
P0501 l17J*1
Vehicle SpeedSensor CircuitMalfunction
Vehicle Speed SensorVehicle Speed Sensor circuitPCM11-135
P0505 (14)ldle ControlSystemMalfunction
IAC valveThrottle BodyFast idle thermo valve*11 ']- 150
P0700P0715PO720P0730P0740P0753P0758
AutomaticTransaxle
Section l4
P1106 (13)BarometricPressure CircuitRange/Performance Problem
ECM/PCM (Baro sensor)
11-137
P1107 (13)BarometricPressure CircuitLow InPut
. ECM/PCM {Baro sensor)11-137
P1108 (13)BarometricPressure CircuitHigh Inpur
ECM/PCM {Baro sensor)11,137
P1121 (7)Throttle PositionLower ThanExpected
. TP sensor11-109
P1122 (7)Throttle PositionHigher ThanExpected
' TP sensor1 1-'109
P112a (5)Manifold AbsolutePressure Lower ThanExpected
. MAP sensor11-94
P1129 (5)Manifold AbsolutePressure HiqherThanExpected
' MAP sensor1l-94
P1297 (20)Electrical LoadDetector CircuitLow Input
Electrical Load DetectorElectrical Load Detector circuitECM/PCM1 1- 138
P1298 (20)Electrical LoadDetector CircuitHigh Input
Electrical Load DetectorElectrical Load Detector circuitECM/PCM11-140
P1300'3
P0301P0302P0303P0304
7l721314
Random lvlisfirelgnition systemFuel supply systemMAP sensorIAC valveContaminated fuelLack offuel
11-126
*: These DTCS will be indicated by the blinking of the Malfunction Indicator Lamp {MlL} with the SCS service connector
connected.**:The E (E])+s indicator light and the Malfunction Indicator Lamp (MlL) may come on simultaneously.*1:A,./T "3: '97 model +5: '99 - 00 models*2: M/T *4:'98 model
{cont'd)
11-77
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PGM-FI System
System Description
INPUTS
CKP/TDC/CYP Sensor
CKF Sensor
MAP Sensor
ECT Sensor
IAT Sensor
TP Sensor
Primary HO2S
Secondary H02S
vss
KS*5
BARO Sensor
ELD*6
Starter Signal
ALT FR Signal
Air Conditioning Signal
Ay'T Gear Position Signal*1
Baftery Voltage (lGN.1)
Brake Switch Signal
PSP Switch Signal
Fuel Tank Pressuae Sensor*4. *5
Countershaft Speed Sensor*1
Mainshaft Speed Sensor*r
OVER-DRIVE Switch Signal*s
ENGINE CONTROL MODULE (ECM)/
POWERTRAIN CONTROL MODULE (PCM) OUTPUTS
|iuel 1"j""- Th,rhg ""d Drrafr";-l
Et*-.nt"tdt"cont.orl
to,r*,c;;trffi;]
l.----.---:. .Lrgnrnon |lmrng Lonrror I
Ecir/PcM B*k',p Fr""il]
m;"t-ll-r*'io*l
Fuel Injectors
PGM-Fl Main Relay (Fuel Pump)
MIL
IAC Valve
Ay'C Compressor Clutch Relay
Radiator Fan Relay
Condenser Fan Relay
ALT
tcM
EVAP Purge Control Solenoid
Valve
Primary HO2S Heater
Secondary H02S HeaterEVAP Bypass Solenoid Valve*a *5
EVAP Control Canister Vent Shut
DLC
Lock-up Control Solenoid Valve*l
Shift Control Solenoid Valve*1
Ay'T Clutch Pressure Control
Solenoid Valve*1
D4 Indicator Light'1 *3, *a
D Indicator Light,l *5
OVER-DRIVE OFF Indicator
Lighl*t *:
*1: A/T {3:'97 model'2: M/f +4:'98 model*5: '99 - 00 models"6: USA
PGM-Fl System
The PGM-Fl system on this model is a sequential multiport fuel injection system.
Fuel iniecior Timing and Duration
The ECM/PCM contains memories for the basic discharge durations at various engine speeds and manifold pressure. The
basic discharge duration, after being read out from the memory, is further modified by signals sent from various sensors
to obtain the final discharge duration.
ldle Air Control
ldle Air Control Valve (lAC Valve)
When the engine is cold, the Ay'C compressor is on, the transmission is in gear, the brake pedal is depressed, the P/S load
is high, or the alternator is charging, the ECM/PCM controls current to the IAC Valve to maintain the correct idle speed.
lgnition Timing Control
o The ECM/PCM contains memories for basic ionition timing at various engine speeds and manifold air flow rates.
lgnition timing is also adjusted for engine coolant temperature.
. A knock control system was adopted which sets the ideal ig nition timing for the octane rating of the gasoline used.*s
Other Control Funstions
1. Starting Control
When the engine is started. the ECM/PCM provides a rich mixture by increasing fuel injector duration.
2. Fuel Pump Control
. When the ignition switch is initially turned on (ll). the ECMiPCM suppli€s ground to the PGM-FI main relay that
supplies current to the fuel pump for two seconds to pressurize the fuel system.
. When the engine is running, the ECM/PCM supplies ground to the PGM-FI main relay that supplies current to the
fuel oumo.
. When the engine is not running and the ignition is on, the ECM/PCM cuts ground to the PGM-FI main relay which
cuts current to the fuel pump.
1 1-80
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Fuel Cut-off Control
. During deceleration with the throttle valve closed, current to the fuel injectors iscutoffto improvefuel economyat
speeds over 970 rpm ('97 - 98 models), 920 rpm ('99 - 00 modelsl.
. Fuel cut-off action also takes place when engine speed exceeds 6,500 rpm ('97 - 98 models), 6900 rpm ('99 - 00
models), regardless of the position of the throttle valve, to protect the engine from over-rewing.
With Ay'T model. the PCM cuts the fuel at engine speeds over 5,000 rpm when the vehicle is not moving.*'
4,./C Comoressor Clutch Relav
When the ECM/PCM receives a demand for cooling from the air conditioning system, it delays the compressor from
being energized, and enriches the mixture to assure a smooth transition to the Ay'C mode.
Evaporative Emission (EVAP) Purge Control Solenoid Valve
When the engine coolant temperature is above 154"F (68'C), the ECM/PCM controls the EVAP purge control solenoid
valve which controls vacuum to the EVAP purge control canister,
Alternator Control
The system controls the voltage generated at the alternator in accordance with the electrical load and driving mode.
which reduces the engine load to improve the fuel economy.
PCM Fail-saf e/Back-up Functions
1. Fail-safe Function
When an abnormality occurs in a signal from a sensor, the ECM/PCM ignores that signal and assumes a pre-pre
grammed value for that sensor that allows the engine to continue to run.
2. Back-up Function
When an abnormality occurs in the ECM/PCM itself, the fuel injectors are controlled by a back-up circuit independent
of the system in order to permit minimal driving.
3. Self-diagnosis Function IMalfunction Indicator Lamp (MlL)l
When an abnormality occurs in a signal from a sensor, the ECM/PCM supplies ground for the MIL and stores the DTC
in erasable memory. When the ignition is initially turned on {ll), the ECM/PCM supplies ground for the MIL for two
seconds to check the MIL bulb condition.
4. Two Trio Detection Method
To prevent false indications, the Two Trip Detection Method is used for the HO2S*1, fuel metering-related. idle control
system, ECT sensor and EVAP control system self-diagnostic functions. When an abnormality occurs, the ECM/PCM
stores it in its memory. When the same abnormality recurs after the ignition switch is turned OFF and ON (ll) again,
the ECM/PCM informs the driver by lighting the MlL. However, to ease troubleshooting, this function is cancelled
when you jump the service check connector, The MIL will then blink immediately when an abnormality occurs.
5. Two (or Three) Driving Cycle Detection Method {'97 model)
A "Driving Cycle" consists of starting the engine, beginning closed loop operation, and stopping the engine. lf misfir-
ing that increases emissions or EVAP control system malfunction is detected during two consecutive driving cycles.
or TWC deterioration is detected during three consecutive driving cycles, the ECM/PCM turns the MIL on. However, to
ease troubleshooting, this function is cancelled when you jump the service check connector. The MIL will then blink
immediately when an abnormality occurs.
*1: '97 - 98 models*2: '99 - 00 models
5.
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ldle Control System
System Description
The idle speed of the engjne 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 by the
ECM/PCM. When the lAc valve is activated, the valve opens to maintain the proper idle speed.
YEL/ From PGM'FI
BLK TMAIN RELAY
VARIOUSSENSORS
4.
IAC VALVE
INTAKE MANIFOLD
After the engine starts, the IAC valve opens for a certain time. The amount of air is increased to raise the idle speed
about 150 - 300 rpm.
when the cootant temperature ts row, the lAc valve is opened to obtain the proper fast idle speed The amount o{
bvoassed air is thus controlled in relation to the engine coolant temperature
When the idle speed is out o{ specification and the scan tool does not indicate Diagnostic Trouble Code (DTC) P0505
or P1508, check the following items:
. Adjust the idle speed (see page 11-169, 170)
. Air conditioning signal (seepagell-1551
. ALT FR signal (see page 1l-159)
. Starter switch signal (see page 11-16'1)
. A,/T gear position signal (see section 14)
. PSP switch signal (seepagell-162)
. Brake switch signal (see page 11-165)
. Fast idlethermovalve (see page'11 168)
. Hoses and connecttons. IAC valve and its mounting O-rings
lf the above items are normat, suDslitute a known-good IAC valve and readjust the idle speed {see page 11-169, 170)
lf the idle speed still cannot be adjusted to specification (and the scan tool does not indicate DTC P0505 or Pl508)
after IAC valve reolacement, substitute a known-good ECM/PCM and recheck lf symptom goes away' replace the
original ECM/PCM.
11-149
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