Infiniti QX4 (R50). Manual — part 171
On Board Diagnosis Logic
NBEC0053
Malfunction is detected when
(Malfunction A) an excessively high voltage from the sensor is
sent to ECM when engine is not running,
(Malfunction B) an excessively low voltage from the sensor is sent
to ECM when engine is running,
(Malfunction C) a high voltage from the sensor is sent to ECM
under light load driving condition,
(Malfunction D) a low voltage from the sensor is sent to ECM
under heavy load driving condition,
(Malfunction E) a voltage from the sensor is constantly approx.
1.0V when engine is running.
FAIL-SAFE MODE
NBEC0053S02
When the malfunction B is detected, the ECM enters fail-safe mode
and the MIL lights up.
Detected items
Engine operating condition in fail-safe mode
Mass air flow sensor circuit
Engine speed will not rise more than 2,400 rpm due to the fuel cut.
Possible Cause
NBEC0426
MALFUNCTION A OR C
NBEC0426S01
I
Harness or connectors
(The sensor circuit is open or shorted.)
I
Mass air flow sensor
MALFUNCTION B, D OR E
NBEC0426S02
I
Harness or connectors
(The sensor circuit is open or shorted.)
I
Intake air leaks
I
Mass air flow sensor
DTC Confirmation Procedure
NBEC0054
Perform “PROCEDURE FOR MALFUNCTION A” first.
If the 1st trip DTC cannot be confirmed, perform “PROCE-
DURE FOR MALFUNCTION B AND E”.
If there is no problem on “PROCEDURE FOR MALFUNCTION
B AND E”, perform “PROCEDURE FOR MALFUNCTION C”.
If there is no problem on “PROCEDURE FOR MALFUNCTION
C”, perform “PROCEDURE FOR MALFUNCTION D”.
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.
GI
MA
EM
LC
FE
AT
TF
PD
AX
SU
BR
ST
RS
BT
HA
SC
EL
IDX
DTC P0100 MASS AIR FLOW SENSOR (MAFS)
On Board Diagnosis Logic
EC-151
SEF058Y
PROCEDURE FOR MALFUNCTION A
NBEC0054S01
With CONSULT-II
NBEC0054S0101
1)
Turn ignition switch “ON”.
2)
Select “DATA MONITOR” mode with CONSULT-II.
3)
Wait at least 6 seconds.
4)
If 1st trip DTC is detected, go to “Diagnostic Procedure”,
EC-155.
With GST
NBEC0054S0102
Follow the procedure “With CONSULT-II” above.
SEF058Y
PROCEDURE FOR MALFUNCTION B AND E
NBEC0054S02
With CONSULT-II
NBEC0054S0201
1)
Turn ignition switch “ON”.
2)
Select “DATA MONITOR” mode with CONSULT-II.
3)
Start engine and wait 5 seconds at most.
4)
If 1st trip DTC is detected, go to “Diagnostic Procedure”,
EC-155.
With GST
NBEC0054S0202
Follow the procedure “With CONSULT-II” above.
NOTE:
If 1st trip DTC is confirmed after more than 5 seconds, there may
be malfunction C.
SEF174Y
PROCEDURE FOR MALFUNCTION C
NBEC0054S03
NOTE:
If engine will not start or stops soon, wait at least 10 seconds with
engine stopped (Ignition switch “ON”) instead of running engine at
idle speed.
With CONSULT-II
NBEC0054S0301
1)
Turn ignition switch “ON”.
2)
Select “DATA MONITOR” mode with CONSULT-II.
3)
Start engine and warm it up to normal operating temperature.
4)
Run engine for at least 10 seconds at idle speed.
5)
If 1st trip DTC is detected, go to “Diagnostic Procedure”,
EC-155.
With GST
NBEC0054S0302
Follow the procedure “With CONSULT-II” above.
DTC P0100 MASS AIR FLOW SENSOR (MAFS)
DTC Confirmation Procedure (Cont’d)
EC-152
SEF243Y
SEF175Y
PROCEDURE FOR MALFUNCTION D
NBEC0054S04
CAUTION:
Always drive vehicle at a safe speed.
With CONSULT-II
NBEC0054S0402
1)
Turn ignition switch “ON”.
2)
Start engine and warm it up to normal operating temperature.
If engine cannot be started, go to “Diagnostic Procedure”,
EC-155.
3)
Select “DATA MONITOR” mode with CONSULT-II.
4)
Check the voltage of MAS AIR/FL SE with “DATA MONITOR”.
5)
Increases engine speed to about 4,000 rpm.
6)
Monitor the linear voltage rise in response to engine speed
increases.
If NG, go to “Diagnostic Procedure”, EC-155.
If OK, go to following step.
7)
Maintain the following conditions for at least 10 consecutive
seconds.
ENG SPEED
More than 2,000 rpm
THRTL POS SEN
More than 3V
Selector lever
Suitable position
Driving location
Driving vehicle uphill (Increased engine load)
will help maintain the driving conditions
required for this test.
8)
If 1st trip DTC is detected, go to “Diagnostic Procedure”,
EC-155.
SEF534P
Overall Function Check
NBEC0055
PROCEDURE FOR MALFUNCTION D
NBEC0055S01
Use this procedure to check the overall function of the mass air flow
sensor circuit. During this check, a 1st trip DTC might not be con-
firmed.
With GST
NBEC0055S0101
1)
Start engine and warm it up to normal operating temperature.
2)
Select “MODE 1” with GST.
3)
Check the mass air flow sensor signal with “MODE 1”.
4)
Check for linear mass air flow sensor signal value rise in
response to increases to about 4,000 rpm in engine speed.
5)
If NG, go to “Diagnostic Procedure”, EC-155.
GI
MA
EM
LC
FE
AT
TF
PD
AX
SU
BR
ST
RS
BT
HA
SC
EL
IDX
DTC P0100 MASS AIR FLOW SENSOR (MAFS)
DTC Confirmation Procedure (Cont’d)
EC-153
Wiring Diagram
NBEC0056
MEC942C
DTC P0100 MASS AIR FLOW SENSOR (MAFS)
Wiring Diagram
EC-154
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