Page 753 of 3051

SEF074X
Overall Function CheckNLEC0242Use this procedure to check the overall function of the three way
catalyst. During this check, a 1st trip DTC might not be confirmed.
Without CONSULT-II
1) Start engine and drive vehicle at a speed of more than 70 km/h
(43 MPH) for 2 consecutive minutes.
2) Stop vehicle with engine running.
3) Set voltmeters probes between ECM terminals 62 (HO2S1
signal), 63 (HO2S2 signal) and engine ground.
4) Keep engine speed at 2,000 rpm constant under no load.
5) Make sure that the voltage switching frequency (high & low)
between ECM terminal 63 and engine ground is much less
than that of ECM terminal 62 and engine ground.
Switching frequency ratio = A/B
A: Heated oxygen sensor 2 (rear) voltage switching fre-
quency
B: Heated oxygen sensor 1 (front) voltage switching fre-
quency
This ratio should be less than 0.75.
If the ratio is greater than above, it means three way catalyst
does not operate properly.
NOTE:
If the voltage at terminal 62 does not switch periodically more
than 5 times within 10 seconds at step 4, perform trouble
diagnosis for DTC P0133 first. (See EC-204.)
Diagnostic ProcedureNLEC0243
1 CHECK EXHAUST SYSTEM
Visually check exhaust tubes and muffler for dent.
OK or NG
OK©GO TO 2.
NG©Repair or replace.
DTC P0420 THREE WAY CATALYST FUNCTIONQG18DE
Overall Function Check
EC-328
Page 754 of 3051
2 CHECK EXHAUST AIR LEAK
1. Start engine and run it at idle.
2. Listen for an exhaust air leak before the three way catalyst.
SEF099P
OK or NG
OK©GO TO 3.
NG©Repair or replace.
3 CHECK INTAKE AIR LEAK
Listen for an intake air leak after the mass air flow sensor.
OK or NG
OK©GO TO 4.
NG©Repair or replace.
4 CHECK IGNITION TIMING
Check for ignition timing.
Refer to ªBASIC INSPECTIONº, EC-99.
OK or NG
OK©GO TO 5.
NG©Check camshaft position sensor (PHASE) (EC-302) and crankshaft position sensor
(POS) (EC-295).
DTC P0420 THREE WAY CATALYST FUNCTIONQG18DE
Diagnostic Procedure (Cont'd)
EC-329
Page 755 of 3051

5 CHECK INJECTORS
1. Refer to Wiring Diagram for Injectors, EC-495.
2. Stop engine and then turn ignition switch ªONº.
3. Check voltage between ECM terminals 101, 103, 105 and 107 and ground with CONSULT-II or tester.
SEF075X
Battery voltage should exist.
OK or NG
OK©GO TO 6.
NG©Perform ªDiagnostic Procedureº INJECTOR, EC-497.
6 CHECK IGNITION SPARK
1. Disconnect ignition coil assembly from rocker cover.
2. Connect a known good spark plug to the ignition coil assembly.
3. Place end of spark plug against a suitable ground and crank engine.
4. Check for spark.
SEF575Q
OK or NG
OK©GO TO 7.
NG©Check ignition coil, power transistor and their circuits. Refer to EC-500.
7 CHECK INJECTOR
1. Turn ignition switch ªOFFº.
2. Remove injector assembly. Refer to EC-44.
Keep fuel hose and all injectors connected to injector gallery.
3. Disconnect camshaft position sensor harness connector.
4. Turn ignition switch ªONº.
Make sure fuel does not drip from injector.
OK or NG
OK (Does not drip)©GO TO 8.
NG (Drips)©Replace the injector(s) from which fuel is dripping.
DTC P0420 THREE WAY CATALYST FUNCTIONQG18DE
Diagnostic Procedure (Cont'd)
EC-330
Page 756 of 3051
8 CHECK INTERMITTENT INCIDENT
Perform ªTROUBLE DIAGNOSIS FOR INTERMITTENT INCIDENTº, EC-145.
Trouble is fixed©INSPECTION END
Trouble is not fixed©Replace three way catalyst.
DTC P0420 THREE WAY CATALYST FUNCTIONQG18DE
Diagnostic Procedure (Cont'd)
EC-331
Page 757 of 3051

DescriptionNLEC0248SYSTEM DESCRIPTIONNLEC0248S01
Sensor Input Signal to ECMECM func-
tionActuator
Crankshaft position sensor (POS) Engine speed
EVAP can-
ister purge
controlEVAP canister purge volume
control solenoid valve Camshaft position sensor (PHASE) Engine speed and cylinder number
Mass air flow sensor Amount of intake air
Engine coolant temperature sensor Engine coolant temperature
Battery Battery voltage
Ignition switch Start signal
Closed 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 DESCRIPTIONNLEC0248S02The 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
NLEC0249
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)
QG18DE
Description
EC-332
Page 758 of 3051

ECM Terminals and Reference Value=NLEC0250Specification 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)
14 GY/LEVAP canister purge vol-
ume control solenoid valve[Engine is running]
+Warm-up condition
+Idle speedBATTERY VOLTAGE
(11 - 14V)
[Engine is running]
+Warm-up condition
+2,000 rpm5 - 12V
SEF975W
On Board Diagnosis LogicNLEC0251
DTC No. Malfunction is detected when ... Check Items (Possible Cause)
P0443
0443+An improper voltage signal is sent to ECM through the
valve.+Harness or connectors
(The valve circuit is open or shorted.)
+EVAP canister purge volume control solenoid
valve
DTC Confirmation ProcedureNLEC0252NOTE:
If ªDTC Confirmation Procedureº has been previously conducted,
always turn ignition switch ªOFFº and wait at least 9 seconds
before conducting the next test.
TESTING CONDITION:
Before performing the following procedure, confirm battery
voltage is more than 11V.
SEF058Y
With CONSULT-II
1) Turn ignition switch ªONº.
2) Select ªDATA MONITORº mode with CONSULT-II.
3) Start engine and let it idle for at least 5 seconds.
4) If 1st trip DTC is detected, go to ªDIAGNOSTIC
PROCEDUREº, EC-336.
With GST
Follow the procedure ªWith CONSULT-IIº above.
DTC P0443 EVAP CANISTER PURGE VOLUME CONTROL SOLENOID VALVE
(CIRCUIT)
QG18DE
ECM Terminals and Reference Value
EC-333
Page 759 of 3051
Wiring DiagramNLEC0253MODELS WITH ECM IN ENGINE COMPARTMENTNLEC0253S01
YEC666
DTC P0443 EVAP CANISTER PURGE VOLUME CONTROL SOLENOID VALVE
(CIRCUIT)
QG18DE
Wiring Diagram
EC-334
Page 760 of 3051
MODELS WITH ECM IN CABINNLEC0253S02
YEC886
DTC P0443 EVAP CANISTER PURGE VOLUME CONTROL SOLENOID VALVE
(CIRCUIT)
QG18DE
Wiring Diagram (Cont'd)
EC-335