2001 INFINITI QX4 Factory Service Manual

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Page 881 of 2395

INFINITI QX4 2001 Factory Service Manual 4 CHECK CMPS (PHASE) GROUND CIRCUIT FOR OPEN AND SHORT
1. Check harness continuity between CMPS (PHASE) terminal 1 and engine ground.
Continuity should exist.
2. Also check harness for short to power.

Page 882 of 2395

INFINITI QX4 2001 Factory Service Manual SEF484Y
On Board Diagnosis LogicNBEC0214The ECM monitors the switching frequency ratio of heated oxygen
sensors 1 (front) and 2 (rear).
A warm-up three way catalyst with high oxygen storage capacity
w

Page 883 of 2395

INFINITI QX4 2001 Factory Service Manual SEF344Z
DTC Confirmation ProcedureNBEC0215
SEF345Z
SEF560X
NOTE:
If ªDTC Confirmation Procedureº has been previously conducted,
always turn ignition switch ªOFFº and wait at least 10 seconds
befor

SEF344Z
DTC Confirmation ProcedureNBEC0215
SEF345Z
SEF560X
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-IINBEC0215S01TESTING CONDITION:
IOpen engine hood before conducting the following proce-
dure.
IDo not hold engine speed for more than the 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.
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-349.
SEF329X
SEF330X
Overall Function CheckNBEC0216Use this procedure to check the overall function of the warm-up
three way catalyst. During this check, a 1st trip DTC might not be
confirmed.
CAUTION:
Always drive vehicle at a safe speed.
WITH GSTNBEC0216S011) 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 63 [heated oxy-
gen sensor 1 (front) right bank signal], 62 [heated oxygen
sensor 1 (front) left bank signal] and engine ground, and ECM
terminals 72 [heated oxygen sensor 2 (rear) right bank signal],
71 [heated oxygen sensor 2 (rear) left bank 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 terminals 72 and engine ground, or 71 and
engine ground is very less than that of ECM terminals 63 and
engine ground, or 62 and engine ground.
Switching frequency ratio = A/B
DTC P0420 (RIGHT BANK, -B1), P0430 (LEFT BANK, -B2) THREE WAY
CATALYST FUNCTION
DTC Confirmation Procedure
EC-348

Page 884 of 2395

INFINITI QX4 2001 Factory Service Manual A: Rear heated oxygen sensor voltage switching fre-
quency
B: Front heated oxygen sensor voltage switching fre-
quency
This ratio should be less than 0.75.
If the ratio is greater than above, it means

Page 885 of 2395

INFINITI QX4 2001 Factory Service Manual 4 CHECK IGNITION TIMING
Check the following items. Refer to ªBasic Inspectionº, EC-101.
MTBL0655
OK or NG
OK©GO TO 5.
NG©Follow the ªBasic Inspectionº.
5 CHECK INJECTORS
1. Refer to WIRING DIAGR

Page 886 of 2395

INFINITI QX4 2001 Factory Service Manual 6 CHECK IGNITION SPARK
1. Turn ignition switch ªOFFº.
2. Disconnect ignition coil assembly from rocker cover.
3. Connect a known good spark plug to the ignition coil assembly.
4. Place end of spark

Page 887 of 2395

INFINITI QX4 2001 Factory Service Manual On Board Diagnosis LogicNBEC0218NOTE:
If DTC P0440 is displayed with P1448, perform trouble diagno-
sis for DTC P1448 first. (See EC-573.)
This diagnosis detects leaks in the EVAP purge line using eng

Page 888 of 2395

INFINITI QX4 2001 Factory Service Manual IEVAP purge line rubber tube bent.
IBlocked or bent rubber tube to EVAP control system pressure
sensor
ILoose or disconnected rubber tube
IEVAP canister vent control valve and the circuit
IEVAP canist

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