
DescriptionNLEC1553SYSTEM DESCRIPTIONNLEC1553S01
Sensor Input Signal to ECMECM func-
tionActuator
Crankshaft position sensor Engine speed
EGR vol-
ume controlEGR volume control valve Mass air flow sensor Amount of intake air
Engine coolant temperature sensor Engine coolant temperature
Ignition switch Start signal
Throttle position sensor Throttle position
Vehicle speed sensor Vehicle speed
Battery Battery voltage
Air conditioner switch Air conditioner operation
Power steering oil pressure switch Power steering load signal
Electrical load Electrical load signal
PNP switch Park/Neutral position signal
TCM (Transmission Control Module) Gear position, shifting signal
This system controls flow rate of EGR led from exhaust manifold
to intake manifold. The opening of the EGR by-pass passage in the
EGR volume control valve changes to control the flow rate. A
built-in step motor moves the valve in steps corresponding to the
ECM output pulses. The opening of the valve varies for optimum
engine control. The optimum value stored in the ECM is determined
by considering various engine conditions. The EGR volume control
valve remains close under the following conditions.
+Low engine coolant temperature
+Engine starting
+High-speed engine operation
+Extremely light load engine operation
+Engine idling
+Excessively high engine coolant temperature
+Wide open throttle
+Mass air flow sensor malfunction
+Low battery voltage
SEF551W
DTC P0403 EGR VOLUME CONTROL VALVE (CIRCUIT)
(WHERE FITTED)
SR20DE
Description
EC-841

SEF184UD
On Board Diagnosis LogicNLEC1561The ECM monitors the switching frequency ratio of heated oxygen
sensors 1 (front) and 2 (rear).
A three way catalyst with high oxygen storage capacity will indicate
a low switching frequency of heated oxygen sensor 2 (rear). As
oxygen storage capacity decreases, the heated oxygen sensor 2
(rear) switching frequency will increase.
When the frequency ratio of heated oxygen sensors 1 (front) and
2 (rear) approaches a specified limit value, the three way catalyst
malfunction is diagnosed.
DTC No. Malfunction is detected when ... Check Items (Possible Cause)
P0420+Three way catalyst does not operate properly.
+Three way catalyst does not have enough oxygen stor-
age capacity.+Three way catalyst
+Exhaust tube
+Intake air leaks
+Injectors
+Injector leaks
+Spark plug
+Improper ignition timing
SEF847Y
SEF848Y
SEF560X
DTC Confirmation ProcedureNLEC1562CAUTION:
Always drive vehicle at a safe speed.
NOTE:
If ªDTC Confirmation Procedureº has been previously conducted,
always turn ignition switch ªOFFº and wait at least 10 seconds
before conducting the next test.
With CONSULT-II
TESTING CONDITION:
+Open engine hood before conducting following proce-
dure.
+Do not hold engine speed more than specified minutes
below.
1) Turn ignition switch ªONº.
2) Select ªDTC & SRT CONFIRMATIONº then ªSRT WORK SUP-
PORTº mode with CONSULT-II.
3) Start engine.
4) Rev engine up to 3,000±500 rpm and hold it for 3 consecutive
minutes then release the accelerator pedal completely.
If ªCOMPLETEDº appears on the CONSULT-II screen, go to
step 7.
5) Wait 5 seconds at idle.
6) Rev engine up to 2,500±500 rpm and maintain it until ªINCMPº
of CATALYST changes to ªCMPLTº (it will take approximately
5 minutes.)
If not ªCMPLTº, stop engine and cool it down to less than 70ÉC
(158ÉF) and then retest from step 1.
7) Select ªSELF-DIAG RESULTSº mode with CONSULT-II.
8) Confirm that the 1st trip DTC is not detected.
If the 1st trip DTC is detected, go to ªDiagnostic Procedureº,
EC-849.
DTC P0420 THREE WAY CATALYST FUNCTIONSR20DE
On Board Diagnosis Logic
EC-848

DescriptionNLEC1565SYSTEM DESCRIPTIONNLEC1565S01
Sensor Input Signal to ECMECM func-
tionActuator
Camshaft position sensor Engine speed
EVAP can-
ister purge
controlEVAP canister purge volume
control solenoid valve Mass air flow sensor Amount of intake air
Engine coolant temperature sensor Engine coolant temperature
Battery Battery voltage
Ignition switch Start signal
Throttle position switch Closed throttle position
Throttle position sensor Throttle position
Heated oxygen sensor 1 (front)Density of oxygen in exhaust gas
(Mixture ratio feedback signal)
Vehicle speed sensor Vehicle speed
This system controls flow rate of fuel vapor from the EVAP canis-
ter. The opening of the vapor by-pass passage in the EVAP canis-
ter purge volume control solenoid valve changes to control the flow
rate. The EVAP canister purge volume control solenoid valve
repeats ON/OFF operation according to the signal sent from the
ECM. The opening of the valve varies for optimum engine control.
The optimum value stored in the ECM is determined by consider-
ing various engine conditions. When the engine is operating, the
flow rate of fuel vapor from the EVAP canister is regulated as the
air flow changes.
SEF337U
COMPONENT DESCRIPTIONNLEC1565S02The EVAP canister purge volume control solenoid valve uses a
ON/OFF duty to control the flow rate of fuel vapor from the EVAP
canister. The EVAP canister purge volume control solenoid valve
is moved by ON/OFF pulses from the ECM. The longer the ON
pulse, the greater the amount of fuel vapor that will flow through the
valve.
CONSULT-II Reference Value in Data Monitor
Mode
NLEC1566
MONITOR ITEM CONDITION SPECIFICATION
PURG VOL C/V+Engine: After warming up
+No-loadIdle 0%
Revving engine Ð
DTC P0443 EVAP CANISTER PURGE VOLUME CONTROL SOLENOID VALVE
(CIRCUIT)
SR20DE
Description
EC-852

4 DETECT MALFUNCTIONING PART
Check the following.
+Harness connectors F60, F13
+Harness for open or short between EVAP canister purge volume control solenoid valve and ECM.
©Repair copen circuit or short to ground or short to power in harness or connectors.
5 CHECK EVAP CANISTER PURGE VOLUME CONTROL SOLENOID VALVE
Refer to ªComponent Inspectionº EC-857.
OK or NG
OK©GO TO 6.
NG©Replace EVAP canister purge volume control solenoid valve.
6 CHECK INTERMITTENT INCIDENT
Perform ªTROUBLE DIAGNOSIS FOR INTERMITTENT INCIDENTº, EC-670.
©INSPECTION END
SEF801Y
SEF079X
Component InspectionNLEC1572EVAP CANISTER PURGE VOLUME CONTROL
SOLENOID VALVE
NLEC1572S01With CONSULT-II
1) Start engine.
2) Perform ªPURG VOL CONT/Vº in ªACTIVE TESTº mode with
CONSULT-II. Check that engine speed varies according to the
valve opening.
If OK, inspection end. If NG, go to following step.
3) Check air passage continuity.
Condition
PURG VOL CONT/V valueAir passage continuity
between A and B
100.0% Yes
0.0% No
If NG or operation takes more than 1 second, replace the
EVAP canister purge volume control solenoid valve.
Without CONSULT-II
Check air passage continuity.
ConditionAir passage continuity
between A and B
12V direct current supply between ter-
minalsYe s
No supply No
If NG or operation takes more than 1 second, replace the EVAP
canister purge volume control solenoid valve.
DTC P0443 EVAP CANISTER PURGE VOLUME CONTROL SOLENOID VALVE
(CIRCUIT)
SR20DE
Diagnostic Procedure (Cont'd)
EC-857

DescriptionNLEC1768SYSTEM DESCRIPTIONNLEC1768S01
Sensor Input Signal to ECMECM func-
tionActuator
Camshaft position sensor Engine speed
Idle air
controlIACV-AAC valve Mass air flow sensor Amount of intake air
Engine coolant temperature sensor Engine coolant temperature
Ignition switch Start signal
Throttle position sensor Throttle position
Park/neutral position (PNP) switch Park/neutral position
Air conditioner switch Air conditioner operation
Power steering oil pressure switch Power steering load signal
Battery Battery voltage
Vehicle speed sensor Vehicle speed
Intake air temperature sensor Intake air temperature
Cooling fan Cooling fan operation
Electrical load Electrical load signal
This system automatically controls engine idle speed to a specified
level. Idle speed is controlled through fine adjustment of the
amount of air which by-passes the throttle valve via IACV-AAC
valve. The IACV-AAC valve changes the opening of the air by-pass
passage to control the amount of auxiliary air. This valve is actu-
ated by a step motor built into the valve, which moves the valve in
the axial direction in steps corresponding to the ECM output sig-
nals. One step of IACV-AAC valve movement causes the respec-
tive opening of the air by-pass passage. (i.e. when the step
advances, the opening is enlarged.) The opening of the valve is
varied to allow for optimum control of the engine idling speed. The
camshaft position sensor detects the actual engine speed and
sends a signal to the ECM. The ECM then controls the step posi-
tion of the IACV-AAC valve so that engine speed coincides with the
target value memorized in ECM. The target engine speed is the
lowest speed at which the engine can operate steadily. The opti-
mum value stored in the ECM is determined by takig into consid-
eration various engine conditions, such as during warm up,
deceleration, and engine load (air conditioner, power steering and
cooling fan operation).
SEF937W
COMPONENT DESCRIPTIONNLEC1768S02IACV-AAC ValveNLEC1768S0201The IACV-AAC valve is operated by a step motor for centralized
control of auxiliary air supply. This motor has four winding phases
and is actuated by the output signals of ECM which turns ON and
OFF two windings each in sequence. Each time the IACV-AAC
valve opens or closes to change the auxiliary air quantity, the ECM
sends a pulse signal to the step motor. When no change in the
auxiliary air quantity is needed, the ECM does not issue the pulse
signal. A certain voltage signal is issued so that the valve remains
at that particular opening.
DTC P0505 IDLE AIR CONTROL VALVE (IACV) Ð AUXILIARY AIR CONTROL
(AAC) VALVE
SR20DE
Description
EC-863

CONSULT-II Reference Value in Data Monitor
Mode
NLEC1580
MONITOR ITEM CONDITION SPECIFICATION
IACV-AAC/V+Engine: After warming up
+Air conditioner switch: OFF
+Shift lever: ªNº
+No-loadIdle 5 - 20 steps
2,000 rpm Ð
ECM Terminals and Reference ValueNLEC1581Specification data are reference values and are measured between each terminal and ground.
CAUTION:
Do not use ECM ground terminals when measuring input/output voltage. Doing so may result in dam-
age to the ECM's transistor. Use a ground other than ECM terminals, such as the ground.
TER-
MINAL
NO.WIRE
COLORITEM CONDITION DATA (DC Voltage)
6
7
15
16BR
LG
GY/L
ORIACV-AAC valve[Engine is running]
+Warm-up condition
+Idle speed0.1 - 14V
On Board Diagnosis LogicNLEC1582
DTC No. Malfunction is detected when ... Check Items (Possible Cause)
P0505+An improper voltage signal is sent to ECM through the
valve.+Harness or connectors
(The IACV-AAC valve circuit is open.)
+IACV-AAC valve
SEF058Y
DTC Confirmation ProcedureNLEC1583NOTE:
+If ªDTC Confirmation Procedureº has been previously
conducted, always turn ignition switch ªOFFº and wait at least
10 seconds before conducting the next test.
+If the target idle speed is out of the specified value, per-
form ªIdle Air Volume Learningº, EC-581, before conduct-
ing ªDTC Confirmation Procedureº. For the target idle
speed, refer to ªService Data and Specifications (SDS)º,
EC-1062.
With CONSULT-II
1) Turn ignition switch ªONº.
2) Select ªDATA MONITORº mode with CONSULT-II.
3) Start engine and warm it up to normal operating temperature.
4) Rev engine from idle to 2,000 rpm 20 times.
If 1st trip DTC is detected, go to ªDIAGNOSTIC
PROCEDUREº, EC-867.
With GST
Follow the procedure ªWith CONSULT-IIº above.
DTC P0505 IDLE AIR CONTROL VALVE (IACV) Ð AUXILIARY AIR CONTROL
(AAC) VALVE
SR20DE
CONSULT-II Reference Value in Data Monitor Mode
EC-864

SEF605Y
SEF089X
Component InspectionNLEC1586IACV-AAC VALVENLEC1586S011) Disconnect IACV-AAC valve harness connector.
2) Check IACV-AAC valve resistance.
Condition Resistance
Terminal 2 and terminals 1, 3
20-24W[at 20ÉC (68ÉF)]
Terminal 5 and terminals 4, 6
3) Reconnect IACV-AAC valve harness connector.
4) Remove idle air adjusting unit assembly (IACV-AAC valve is
built-in) from throttle body.
(The IACV-AAC valve harness connector should remain con-
nected.)
5) Turn ignition switch ªONº and ªOFFº, and ensure the IACV-
AAC valve shaft smoothly moves forward and backward,
according to the ignition switch position.
If NG, replace the IACV-AAC valve.
DTC P0505 IDLE AIR CONTROL VALVE (IACV) Ð AUXILIARY AIR CONTROL
(AAC) VALVE
SR20DE
Component Inspection
EC-871

System DescriptionNLEC1618COOLING FAN CONTROLNLEC1618S01
Sensor Input Signal to ECMECM func-
tionActuator
Vehicle speed sensor Vehicle speed
Cooling fan
controlCooling fan relay(s) Engine coolant temperature sensor Engine coolant temperature
Air conditioner switch Air conditioner ªONº signal
Ignition switch Start signal
Refrigerant pressure sensor Refrigerant pressure
The ECM controls the cooling fan corresponding to the vehicle speed, engine coolant temperature, refriger-
ant pressure, and air conditioner ON signal. The control system has 3-step control [HIGH/LOW/OFF].
OPERATIONNLEC1618S02
SEF771Z
CONSULT-II Reference Value in Data Monitor
Mode
NLEC1619Specification data are reference values.
MONITOR ITEM CONDITION SPECIFICATION
AIR COND SIG+Engine: After warming up, idle
the engineAir conditioner switch: OFF OFF
Air conditioner switch: ON
(Compressor operates)ON
DTC P1217 OVERHEAT (COOLING SYSTEM)SR20DE
System Description
EC-882