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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PGM-FI System
Manifold Absolute Pressure (MAPI Sensor
The scan tool indicates Diagnostic Trouble Code (DTC) POl07: A low input (high vacuum) problem in theManifold Absolute Pressure (MAP) sensor,
The MAP sensor convens manifold absolute pressure into electrical signals and inputs the ECM/pCM.
OUTPUIVOLTAGE
tvl3.s
3.0
2.5
2.O
1.5
1.0
0.5
o .5 ro- 15^ 1olin.H9) GAUGEREADIT{G
lmmHgl
3025
100 200 300 a00 5oo 6fi, 7d)
MAP SENSOR 3P CONNECTOR IC131I
vccl(YEL/RED}
Th6 MIL has b€en reoorted on.DTC P0107 is 3tored.
Problom verification:1. Turn the ignition switch ON lll).2. Check the lvlAP with the scanroot.
lrtormittem tailu.e, lystam b OKat thb timo. Check tor poor con-noctions or loosa wird at C131(MAP rensor) and rt the ECM/PCM.
ls approx. 101 kPa (760 mmHg,30 in.Hg),2.9 V indicated?
Check for an op6n in wi.o IVCC1linel:1. Turn the ignition switch OFF.2. Disconnect the MAP sensorconnector,3. Turn the ignition switch ON {ll}.4. Measure voltage between theMAP sensor connector No. 1termanal and No. 2 terminal.
Roprir op€n in the wir6 bstweentho ECM/PCM (D4, C19*l and theMAP sensor.
ls there approx. 5 V?
(To page 11-91)
11-90
Wiro side ol temale terminals
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Throttle Position (TPl Sensor
The scan tool indicates Diagnostic Trouble Code (DTC) P0122: A low input (voltage) problem in the Throttle
Position (TP) sensor circuit.
The TP Sensor is a potentiometer. lt is connocted to the throttle valve shaft. As the throttle position changes, the throftle
position sensor varies the voltage signal to the ECM/PCM.
'97 mod6l:BRUSHHOI,I'ER
OUTPUT VOLTAGE IVI
5
4
3
2
1
0
THROITLEOPCNIiIG
FUTIIHROTTI"E
TP SENSOR 3P CONNECTOR {Cl3OI
vcc2IYEL/BLUI
Wi.6 6ide ot fgmale terminsls
PCM CONNECTOR D I16PI
Wire side of female terminals
(GRN/BLX)
- The MIL h.3 been reoorted on.- OTC m122 b 3tored.
Problem vorificalion:1. Start the engine. Hold theengine at 3,000 rpm with noload (in Park or neutrall untilthe radiator fan comes on,then turn the ignition switchOFF.2. Turn the ignition switch ON (ll).
3. Check the throttle position
with the scan tool.
ls there approx. 10% when thethrottle is fully closed andapprox.90% when the throttleis fully opened?
Intormittent feilu?e, 3y3tem is OKat thb iime. Check tor poor con-nodiona or loose wiros at C130tTP loNorl .nd rt th€ PCM.
Check tor an open in the wire{vOC2linel:1. Turn the ignition switch OFF.2. Disconnect the TP sensor 3Pconnector,3. Turn the ignition switch ON lll).il. Measure voltage betweenthe TP sensor 3P connector ter-minals No. 1 and No. 3.
ls there approx.5 V?
Check to. an open in wir6 {VCC2linel:Measure voltage between PCMconnector terminals 010 and D11.
Ch6ck to. an opon or shon in TPsonaol:1. Turn the ignition switch OFF.2, At the sensor side, measureresistance between the TPsensor 3P connector terminalsNo. 1 and No. 2 with the throt-tle fully closed.
Repair open in the wirc betweenPCM {D10} and TP 3ensor.ls there approx. 5 V?
Sub3tituto . known-good PCMand rechock. It proscribed volt-ag. b now availablo. rcplaco th6originsl PCM,
Terminal side of male terminals(cont'd)
(To page 11-104)
1 1-103
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PGM-FI System
Primary Heated Oxygen Sensor (Primary HO2S) (Sensor 1)
The Heated Oxygen Sensors (HO2S) detect the oxygen content in the exhaust gas and signal the ECM/PCM. In operation,
the ECM/PCM receives the signals from the sensor and varies the duration during which fuel is iniected. To stabilize the
sensor's output, the sensor has an internal heater. The Primary HO2S (Sensor 1) is installed in exhaust pipe A.
HO2S:
ztRcoNtAEI.IMENT
s€NsoRTERMINALSVOLTAGE IVI
HEATEBTERMINALS
The scan tool indicates Diagnostic Trouble Code (DTC) P0131: A low voltage
Oxygen Sensor (HO2S) {Sensor 1} circuit,
RICH - AIR. . LEANFUELNATO
problem in the Primary Heated
37 - 98 models:
HEATER
The MIL has been reoorted on.DTC P0131 is stoied.
Problem verification:1. Do the ECM/PCM Reset Pro-ceoure.Start the engine. Hold theengine at 3,000 rpm with noload (in Park or neutral) untilthe radiator fan comes on.Test-drive with the A/T in Eposition (M/T in 4th gear)Check the Primary HO2S{Sensor 1} output voltage withthe scan tool during accelera-tion using wide open throttle.
Intermittent f.ilure, system is OKat this time. Check fo. poor con-nections or loose wirer at C111(Primary HO2S, SeGor 1) and atrh€ ECM/FCM.
Check the fuel pressure (see page
11-178).
Repair the fuel supply system.
{To page 11'111}
1 1-1 10
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tro-rsl
1Tffi61
tF136t
fPfa6r-1
tF138tl
I-Pi382l
Crankshaft Position/Top Dead Genter/Gylinder Position (CKP/TDC/CYPI Sensor
The scan tool indicates Diagnostic Trouble Code (DTC) P0335; A malfunction in the Crankshaft Position (CKP)
sensor circuit,
The scan tool indicates Diagnostic Trouble Code (DTC) P0336: A range/performance problem in the Crankshaft
Position {CKP) sensor circuit.
The scan tool indicates Diagnostic Trouble Code {DTC) P1361: Intermittent interruption in the Top Dead Center
(TDC) sensor circuit.
The scan tool indicates Diagnostic Trouble Code (DTC) P1362: No signal in the Top Dead Center (TDC) sensor
ci.cuit.
The scan tool indicates Diagnostic Trouble Code (DTC) P1381: Intermittent interruption in the Cylinder Position
(CYP) sensor circuit.
The scan toot indicates Diagnostic Trouble Code {DTC) P1382: No signal in the Cylinder Position (CYP} sensor
circuit.
Description
The CKP Sensor determines timing for fuel injection and ignition of each cylinder and also detects engine speed. The TDC
Sensor determines ignition timing at start-up {cranking) and when crank angle is abnormal. The CYP Sensor detects the
position of No. 't cylinder for sequential fuel injection to each cylinder. The CKP/TDC/CYP Sensor is built into the distribu-
ror.
NOTE: lf DTC P1359 is stored atthesametimeas DTC P0335, P0336, Pl361, P1362, P1381 and/or P1382, troubleshoot DTC
P1359 first, then troubleshoot those DTCS.
DISTRIBUTOR lOPCoNNECTOR (Cl211
TDCP IGRNI
Terminal side ofmale terminalsTIrcM IREOI
'97 model:
- The MIL has be€n reported on.- DTC P0335, P0336, P136' 1,P1362, Pl341 and/oi P1382 arestored.
Problem verific.tion:1. Do the PCM Reset Procedure.2. Start the engine.
Intermittent lailure, 3yd6m i3 OKat thb tims. Chcck tor poor con-nections ol looso wire3 si C12'l
ldistributor) .nd .t the PCM.
ls DTC P0335, P0336, P1361, P1362,P1381 and/or P1382 indicated?
Ch.ck for an open in tho CKP/TDC/CYP sensor:1. Turn the ignition switch OFF.2. Disconnect the distributor 10Pconnector.3. Measure resistance betweenthe terminals of the indicatedsensor (see table).
Replace tho distributor ignitionhousing {sea 3ection 41.ls there 350 - 700 o?
(To page 11-132)
CYPP IYELI
CYPM (BLKI
SENSOEDTCSENSOBPCMERMINAIWIRECOLOR
CKPP0335P0336
lc28LU
8c12
TDCP1361P1352
2GRN
9c13RED
CYPP' I381P1342
3c4YEL't0c14BLK
{cont'd)
11-131
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PGM-FI System
Grankshaft Speed Fluctuation (CKF) Sensor
fF13361l Tj":""l.tool indicates Diagnostic Trouble Code (DTCI P1336: Intermittent interruption inthe Crankshaft Speed: Fluctuation (CKF) sensor circuit.
The scan tool indicates Diagnostic Trouble Code (DTC) P1337: No signal in the Crankshaft Speed Fluctuation (CKF)
sensor circuit.
Description
The diagnostic system has a pulser rotor on the crankshaft and a pulse pick-up sensor on the engine block. The ECM/PCM
monitors the crankshaft speed fluctuation based on the CKF sensor signal, and judges that an engine misfire occurred if
the fluctuation goes beyond a predetermined limit.
37 mod.l:
CKF SENSOR 2P CONNECTOR IClO4I
T:]l-r'r Lll
l1 zLl''''CKF P I lcKF Mtalu/aeot fdJ twxrneor\-7
Terminal side of male terminals
(To page 11-113)
11-142
- Tho MIL ha3 been reported on.- DTC P1336 and/or P1337 arestored.
Problem verificrtion:1. Do the PCM Reset Procedure.2. Start the engine.
Intermittent {ailure, systom is OK.l thia timo. Ch6ck tor poor con-nections or loose wir$ at ClorlICKF sonsorl .nd at tho PCM.
Chock tor an opon in th6 CKF .en'30r:1. Turn the ignition switch OFF.2. Disconnect the CKF sensor 2Pconnector,3, M easure the resistancebetween the CKF sensor 2Pconnector terminals No. 'l andNo.2.
ls there 1.6-3.2 kO?
Check fo. a short in the CKF 3en-sot:Check for continuity betweenbody ground and the CKF sensor2P connector terminals No. 1 andNo.2 individually.
CKF SENSOR
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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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ldle Control System
ldle Air Control llAC) Valve
The scan tool indicates Diagnostic Trouble Code (DTC) Pl508: A probtem in the ldle Air Controt flAC) varvecircuit.
The IAC Valve changes the amount of air bypassing the throttle body in response to a current signal from the ECM/PCM inorder to maintain the proper idle speed.
37 model;
IAC VALVE 2P CONNECTOR {C132}
,f rcp'# IYEL/BI.(II2f-1-d)
Y
Wir€ side of female terminals
PCM CONNECTOR A I32PI
tacvIBLK/BLU)
From AIR To INTAKECLEANER MANIFOLD
Wire side of female terminals
The MIL has beon .eport€d on.OIC Pl508 is sto.ed.
Problem veiification:1. Do the PCM Reset Procedure.2. Start the engine, and warm itup to normal operating tem-perature.
Inte.mittent failure, systcm b OKat thi3 time. Check tor poo. con-nections or loose wircs at C132(lAC v.lvel and at the PCM.
ls DTC Pl508 indicated?
Check lor an open in the wir6{lGPl lins}:1. Turn the ignition switch OFF.2. Disconnect the IAC valve 2Pconnector.3. Turn the ignition switch ON {ll).4. Measure voltage between bodyground and the IAC valve 2Pconnector term inal No.2.
Repair open in the wire trctwoontha IAC v!lv6 and the PGM-Flmain relly.
Chock for an opan o. short in thowi.e (lACv linel:1. Turn the ignition switch OFFand reconnect the IAC valve2P connector.2. Disconnect the PCM conneclorA (32P).
3. Turn the ignition switch ON {ll).4, Measure voltage betweenbody ground and PCM con-nector terminal A12.
{To page 1l-153)
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