INFINITI QX4 2001 Factory Service Manual

ICrankshaft position sensor (REF)
ICrankshaft position sensor (POS)
IMass air flow sensor
MALFUNCTION CNBEC0430S03IHarness or connectors
(The throttle position sensor circuit is open or shorted.)
IIntake air leaks
IThrottle position sensor
DTC Confirmation ProcedureNBEC0078NOTE:
IPerform ªPROCEDURE FOR MALFUNCTION Aº first. If the
1st trip DTC cannot be confirmed, perform ªPROCEDURE
FOR MALFUNCTION Bº.
If there is no problem on ªPROCEDURE FOR MALFUNC-
TION Bº, perform ªPROCEDURE FOR MALFUNCTION Cº.
IIf ªDTC Confirmation Procedureº has been previously
conducted, always turn ignition switch ªOFFº and wait at least
10 seconds before conducting the next test.
PROCEDURE FOR MALFUNCTION ANBEC0078S01CAUTION:
Always drive vehicle at a safe speed.
TESTING CONDITION:
IBefore performing the following procedure, confirm that
battery voltage is more than 10V at idle.
IThis test may be conducted with the drive wheels lifted in
the shop or by driving the vehicle. If a road test is
expected to be easier, it is unnecessary to lift the vehicle.
SEF065Y
With CONSULT-IINBEC0078S01011) Turn ignition switch ªONº and select ªDATA MONITORº mode
with CONSULT-II.
2) Start engine and maintain the following conditions for at least
5 consecutive seconds.
Vehicle speed More than 5 km/h (3 MPH)
Selector lever Suitable position except ªPº or ªNº position
3) If 1st trip DTC is detected, go to ªDiagnostic Procedureº,
EC-181.
With GSTNBEC0078S0102Follow the procedure ªWith CONSULT-IIº above.
DTC P0120 THROTTLE POSITION SENSOR
Possible Cause (Cont'd)
EC-176

SEF058Y
PROCEDURE FOR MALFUNCTION BNBEC0078S02With CONSULT-IINBEC0078S02011) Turn ignition switch ªONº.
2) Select ªDATA MONITORº mode with CONSULT-II.
3) Start engine and let it idle for at least 10 seconds.
If idle speed is over 1,000 rpm, maintain the following condi-
tions for at least 10 seconds to keep engine speed below 1,000
rpm.
Selector lever Suitable position except ªPº or ªNº
Brake pedal Depressed
Vehicle speed 0 km/h (0 MPH)
4) If 1st trip DTC is detected, go to ªDiagnostic Procedureº,
EC-181.
With GSTNBEC0078S0202Follow the procedure ªWith CONSULT-IIº above.
SEF177Y
PROCEDURE FOR MALFUNCTION CNBEC0078S03CAUTION:
Always drive vehicle at a safe speed.
With CONSULT-IINBEC0078S03011) Start engine and warm it up to normal operating temperature.
2) Turn ignition switch ªOFFº and wait at least 10 seconds.
3) Turn ignition switch ªONº.
4) Select ªMANU TRIGº in ªDATA MONITORº mode with CON-
SULT-II.
5) Select ªTHRTL POS SENº and ªABSOL TH´P/Sº in ªDATA
MONITORº mode with CONSULT-II.
6) Press RECORD on CONSULT-II SCREEN at the same time
accelerator pedal is depressed.
7) Print out the recorded graph and check the following:
IThe voltage rise is linear in response to accelerator pedal
depression.
IThe voltage when accelerator pedal is fully depressed is
approximately 4V.
If NG, go to ªDiagnostic Procedureº, EC-181.
If OK, go to following step.
GI
MA
EM
LC
FE
AT
TF
PD
AX
SU
BR
ST
RS
BT
HA
SC
EL
IDX
DTC P0120 THROTTLE POSITION SENSOR
DTC Confirmation Procedure (Cont'd)
EC-177

SEF174Z
8) Select ªAUTO TRIGº in ªDATA MONITORº mode with CON-
SULT-II.
SEF178Y
9) Maintain the following conditions for at least 10 consecutive
seconds.
ENG SPEED More than 2,000 rpm
MAS A/F SE-B1 More than 3.2V
COOLAN TEMP/S More than 70ÉC (158ÉF)
Selector lever Suitable position
Driving location Driving vehicle uphill (Increased engine load)
will help maintain the driving conditions
required for this test.
10) If 1st trip DTC is detected, go to ªDiagnostic Procedureº,
EC-181.
DTC P0120 THROTTLE POSITION SENSOR
DTC Confirmation Procedure (Cont'd)
EC-178

SEF305X
With GST=NBEC0078S03021) Start engine and warm it up to normal operating temperature.
2) Maintain the following conditions for at least 10 consecutive
seconds.
Gear position Suitable position
Engine speed More than 2,000 rpm
Engine coolant temperature More than 70ÉC (158ÉF)
Voltage between ECM termi-
nal 91 (Mass air flow sensor
signal) and groundMore than 3.2V
3) Select ªMODE 7º with GST.
4) If 1st trip DTC is detected, go to ªDiagnostic Procedureº,
EC-181.
GI
MA
EM
LC
FE
AT
TF
PD
AX
SU
BR
ST
RS
BT
HA
SC
EL
IDX
DTC P0120 THROTTLE POSITION SENSOR
DTC Confirmation Procedure (Cont'd)
EC-179

Wiring DiagramNBEC0079
MEC946C
DTC P0120 THROTTLE POSITION SENSOR
Wiring Diagram
EC-180

Diagnostic ProcedureNBEC0080
1 INSPECTION START
Which malfunction A, B or C is duplicated?
MTBL0066
TypeA,BorC
TypeAor B©GO TO 4.
Type C©GO TO 2.
2 ADJUST THROTTLE POSITION SENSOR
Check the following items. Refer to ªBasic Inspectionº, EC-101.
MTBL0655
©GO TO 3.
3 CHECK INTAKE SYSTEM.
1. Turn ignition switch ªOFFº.
2. Check the following for connection.
IAir duct
IVacuum hoses
IIntake air passage between air duct to intake manifold collector
OK or NG
OK©GO TO 4.
NG©Reconnect the parts.
4 RETIGHTEN GROUND SCREWS
1. Turn ignition switch ªOFFº.
2. Loosen and retighten engine ground screws.
SEF959Y
©GO TO 5.
GI
MA
EM
LC
FE
AT
TF
PD
AX
SU
BR
ST
RS
BT
HA
SC
EL
IDX
DTC P0120 THROTTLE POSITION SENSOR
Diagnostic Procedure
EC-181

5 CHECK THROTTLE POSITION SENSOR POWER SUPPLY CIRCUIT
1. Disconnect throttle position sensor harness connector.
SEF944Y
2. Turn ignition switch ªONº.
3. Check voltage between throttle position sensor terminal 1 and ground with CONSULT-II or tester.
SEF964Y
OK or NG
OK©GO TO 6.
NG©Repair open circuit or short to ground or short to power in harness or connectors.
6 CHECK THROTTLE POSITION SENSOR GROUND CIRCUIT FOR OPEN AND SHORT
1. Turn ignition switch ªOFFº.
2. Check harness continuity between sensor terminal 3 and engine ground.
Refer to Wiring Diagram.
Continuity should exist.
3. Also check harness for short to power.
OK or NG
OK©GO TO 8.
NG©GO TO 7.
7 DETECT MALFUNCTIONING PART
Check the following.
IHarness for open or short between ECM and throttle position sensor
IHarness for open or short between TCM (Transmission Control Module) and throttle position sensor
©Repair open circuit or short to power in harness or connectors.
DTC P0120 THROTTLE POSITION SENSOR
Diagnostic Procedure (Cont'd)
EC-182

8 CHECK THROTTLE POSITION SENSOR INPUT SIGNAL CIRCUIT FOR OPEN AND SHORT
1. Disconnect ECM harness connector.
2. Check harness continuity between ECM terminal 91 and throttle position sensor terminal 2.
Refer to Wiring Diagram.
Continuity should exist.
3. Also check harness for short to ground and short to power.
OK or NG
OK (With CONSULT-II)©GO TO 9.
OK (Without CONSULT-
II)©GO TO 10.
NG©Repair open circuit or short to ground or short to power in harness or connectors.
9 CHECK THROTTLE POSITION SENSOR
With CONSULT-II
1. Start engine and warm it up to normal operating temperature.
2. Stop engine (ignition switch OFF).
3. Remove the vacuum hose connected to the throttle opener.
4. Connect suitable vacuum hose to the vacuum pump and the opener.
5. Apply vacuum [more than ±40.0kPa (±300mmHg, ±11.81inHg)] until the throttle drum becomes free from the rod of the
throttle opener.
SEF793W
6. Turn ignition switch ON.
7. Select ªDATA MONITORº mode with CONSULT-II.
8. Check voltage of ªTHRTL POS SENº under the following conditions.
Voltage measurement must be made with throttle position sensor installed in vehicle.
SEF062Y
OK or NG
OK©GO TO 12.
NG©GO TO 11.
GI
MA
EM
LC
FE
AT
TF
PD
AX
SU
BR
ST
RS
BT
HA
SC
EL
IDX
DTC P0120 THROTTLE POSITION SENSOR
Diagnostic Procedure (Cont'd)
EC-183

10 CHECK THROTTLE POSITION SENSOR
Without CONSULT-II
1. Start engine and warm it up to normal operating temperature.
2. Stop engine (ignition switch OFF).
3. Remove the vacuum hose connected to the throttle opener.
4. Connect suitable vacuum hose to the vacuum pump and the opener.
5. Apply vacuum [more than þ40.0 kPa (þ300 mmHg, þ11.81 inHg)] until the throttle drum becomes free from the rod of
the throttle opener.
SEF793W
6. Turn ignition switch ON.
7. Check voltage between ECM terminal 91 (Throttle position sensor signal) and ground.
Voltage measurement must be made with throttle position sensor installed in vehicle.
MTBL0231
OK or NG
OK©GO TO 12.
NG©GO TO 11.
11 ADJUST CLOSED THROTTLE POSITION SWITCH
Adjust closed throttle position switch. Refer to ªBasic Inspectionº, EC-101.
MTBL0655
OK or NG
OK©GO TO 12.
NG©Replace throttle position sensor. To adjust it, perform ªBasic Inspectionº, EC-101.
DTC P0120 THROTTLE POSITION SENSOR
Diagnostic Procedure (Cont'd)
EC-184

12 CHECK MASS AIR FLOW SENSOR
1. Reconnect harness connectors disconneted.
2. Start engine and warm it up to normal operating temperature.
3. Check voltage between ECM terminal 61 (Mass air flow sensor signal) and ground.
SEF298X
4. If the voltage is out of specification, disconnect mass air flow sensor harness connector and connect it again.
Then repeat above check.
OK or NG
OK©GO TO 13.
NG©Replace mass air flow sensor.
13 CHECK CRANKSHAFT POSITION SENSOR (POS)
1. Install all removed parts.
2. Perform ªDTC Confirmation Procedureº for DTC P0335 and P1336. Refer to EC-336, 519.
OK or NG
OK©GO TO 14.
NG©Replace crankshaft position sensor (POS).
14 CHECK CRANKSHAFT POSITION SENSOR (REF)
Perform ªDTC Confirmation Procedureº for DTC P1335. Refer to EC-511.
OK or NG
OK©GO TO 15.
NG©Replace crankshaft position sensor (REF).
GI
MA
EM
LC
FE
AT
TF
PD
AX
SU
BR
ST
RS
BT
HA
SC
EL
IDX
DTC P0120 THROTTLE POSITION SENSOR
Diagnostic Procedure (Cont'd)
EC-185