Infiniti QX4 (R50). Manual — part 220
SEF484Y
On Board Diagnosis Logic
NBEC0214
The 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
will indicate a low switching frequency of rear heated oxygen sen-
sor. As oxygen storage capacity decreases, the rear heated oxy-
gen sensor switching frequency will increase.
When the frequency ratio of front and rear heated oxygen sensors
approaches a specified limit value, the warm-up three way catalyst
malfunction is diagnosed.
Malfunction is detected when warm-up three way catalyst does not
operate properly, warm-up three way catalyst does not have
enough oxygen storage capacity.
Possible Cause
NBEC0504
I
Warm-up three way catalyst
I
Exhaust tube
I
Intake air leaks
I
Injectors
I
Injector leaks
I
Spark plug
I
Improper ignition timing
GI
MA
EM
LC
FE
AT
TF
PD
AX
SU
BR
ST
RS
BT
HA
SC
EL
IDX
DTC P0420 (RIGHT BANK, -B1), P0430 (LEFT BANK, -B2) THREE WAY
CATALYST FUNCTION
On Board Diagnosis Logic
EC-347
SEF344Z
DTC Confirmation Procedure
NBEC0215
SEF345Z
SEF560X
NOTE:
If “DTC Confirmation Procedure” has been previously conducted,
always turn ignition switch “OFF” and wait at least 10 seconds
before conducting the next test.
WITH CONSULT-II
NBEC0215S01
TESTING CONDITION:
I
Open engine hood before conducting the following proce-
dure.
I
Do not hold engine speed for more than the specified
minutes below.
1)
Turn ignition switch “ON”.
2)
Select “DTC & SRT CONFIRMATION” then “SRT WORK SUP-
PORT” 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 “INCMP”
of CATALYST changes to “CMPLT” (It will take approximately
5 minutes).
If not “CMPLT”, stop engine and cool it down to less than 70°C
(158°F) and then retest from step 1.
7)
Select “SELF-DIAG RESULTS” mode with CONSULT-II.
8)
Confirm that the 1st trip DTC is not detected.
If the 1st trip DTC is detected, go to “Diagnostic Procedure”,
EC-349.
SEF329X
SEF330X
Overall Function Check
NBEC0216
Use 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 GST
NBEC0216S01
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 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
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 warm-up three way
catalyst does not operate properly. Go to “Diagnostic
Procedure”, EC-349.
NOTE:
If the voltage at terminal 62 or 63 does not switch periodically more
than 5 times within 10 seconds at step 5, perform trouble diagno-
sis for “DTC P0133, P0153” first. (See EC-218.)
Diagnostic Procedure
NBEC0217
1
CHECK EXHAUST SYSTEM
Visually check exhaust tubes and muffler for dent.
OK or NG
OK
©
GO TO 2.
NG
©
Repair or replace.
2
CHECK EXHAUST AIR LEAK
1. Start engine and run it at idle.
2. Listen for an exhaust air leak before the warm-up 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.
GI
MA
EM
LC
FE
AT
TF
PD
AX
SU
BR
ST
RS
BT
HA
SC
EL
IDX
DTC P0420 (RIGHT BANK, -B1), P0430 (LEFT BANK, -B2) THREE WAY
CATALYST FUNCTION
Overall Function Check (Cont’d)
EC-349
4
CHECK IGNITION TIMING
Check the following items. Refer to “Basic Inspection”, EC-101.
MTBL0655
OK or NG
OK
©
GO TO 5.
NG
©
Follow the “Basic Inspection”.
5
CHECK INJECTORS
1. Refer to WIRING DIAGRAM for Injectors, EC-617.
2. Stop engine and then turn ignition switch “ON”.
3. Check voltage between ECM terminals 101, 102, 103, 104, 105, 107 and ground with CONSULT-II or tester.
SEF331X
OK or NG
OK
©
GO TO 6.
NG
©
Perform “Diagnostic Procedure”, “INJECTOR”, EC-618.
DTC P0420 (RIGHT BANK, -B1), P0430 (LEFT BANK, -B2) THREE WAY
CATALYST FUNCTION
Diagnostic Procedure (Cont’d)
EC-350
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