INFINITI QX4 2001 Factory Service Manual

4 CHECK MAFS POWER SUPPLY CIRCUIT
1. Disconnect mass air flow sensor (MAFS) harness connector.
SEF960Y
2. Turn ignition switch ªONº.
3. Check voltage between MAFS terminals 2, 4 and ground with CONSULT-II or tester.
SEF297X
OK or NG
OK©GO TO 6.
NG©GO TO 5.
5 DETECT MALFUNCTIONING PART
Check the following.
IHarness for open or short between ECM relay and mass air flow sensor
IHarness for open or short between mass air flow sensor and ECM
©Repair harness or connectors.
6 CHECK MAFS GROUND CIRCUIT FOR OPEN AND SHORT
1. Turn ignition switch ªOFFº.
2. Disconnect ECM harness connector.
3. Check harness continuity between MAFS terminal 3 and ECM terminal 73.
Refer to Wiring Diagram.
Continuity should exist.
4. Also check harness for short to power.
OK or NG
OK©GO TO 7.
NG©Repair open circuit or short to power in harness or connectors.
DTC P0100 MASS AIR FLOW SENSOR (MAFS)
Diagnostic Procedure (Cont'd)
EC-156

7 CHECK MAFS INPUT SIGNAL CIRCUIT FOR OPEN AND SHORT
1. Check harness continuity between MAFS terminal 1 and ECM terminal 61.
Refer to Wiring Diagram.
Continuity should exist.
2. Also check harness for short to ground and short to power.
OK or NG
OK©GO TO 8.
NG©Repair open circuit or short to ground or short to power in harness or connectors.
8 CHECK MASS AIR FLOW SENSOR
1. Reconnect harness connectors disconnected.
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 MAFS harness connector and connect it again.
Then repeat above check.
OK or NG
OK©GO TO 9.
NG©Replace mass air flow sensor.
9 CHECK INTERMITTENT INCIDENT
Refer to ªTROUBLE DIAGNOSIS FOR INTERMITTENT INCIDENTº, EC-140.
©INSPECTION END
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DTC P0100 MASS AIR FLOW SENSOR (MAFS)
Diagnostic Procedure (Cont'd)
EC-157

SEF052V
SEF946SB
Component DescriptionNBEC0725The absolute pressure sensor detects ambient barometric pressure
and sends the voltage signal to the ECM. As the pressure
increases, the voltage rises.
ECM Terminals and Reference ValueNBEC0726Specification 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.
TERMI-
NAL
NO.WIRE
COLORITEM CONDITION DATA (DC Voltage)
80 L/RAbsolute pressure sen-
sor[Ignition switch ªONº]Approximately 4.4V
111 P/B Sensors' power supply[Ignition switch ªONº]Approximately 5V
58 B/P Sensors' ground[Engine is running]
IWarm-up condition
IIdle speedApproximately 0V
On Board Diagnosis LogicNBEC0727Malfunction is detected when an excessively low or high voltage
from the sensor is sent to ECM.
DTC P0105 ABSOLUTE PRESSURE SENSOR
Component Description
EC-158

Possible CauseNBEC0728IHarness or connectors
(Absolute pressure sensor circuit is open or shorted.)
IAbsolute pressure sensor
DTC Confirmation ProcedureNBEC0729NOTE:
If ªDTC Confirmation Procedureº has been previously conducted,
always turn ignition switch ªOFFº and wait at least 10 seconds
before conducting the next test.
SEF058Y
WITH CONSULT-IINBEC0729S011) Turn ignition switch ªONº.
2) Select ªDATA MONITORº mode with CONSULT-II.
3) Wait at least 10 seconds.
4) If 1st trip DTC is detected, go to ªDiagnostic Procedureº,
EC-161.
WITH GSTNBEC0729S02Follow the procedure ªWITH CONSULT-IIº above.
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DTC P0105 ABSOLUTE PRESSURE SENSOR
Possible Cause
EC-159

Wiring Diagram=NBEC0730
MEC943C
DTC P0105 ABSOLUTE PRESSURE SENSOR
Wiring Diagram
EC-160

Diagnostic ProcedureNBEC0731
1 RETIGHTEN GROUND SCREWS
1. Turn ignition switch ªOFFº.
2. Loosen and retighten engine ground screws.
SEF959Y
©GO TO 2.
2 CHECK ABSOLUTE PRESSURE SENSOR CONNECTOR FOR WATER
1. Disconnect absolute pressure sensor harness connector.
SEF961Y
2. Check sensor harness connector for water.
Water should not exist.
OK or NG
OK©GO TO 3.
NG©Repair or replace harness connector.
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DTC P0105 ABSOLUTE PRESSURE SENSOR
Diagnostic Procedure
EC-161

3 CHECK ABSOLUTE PRESSURE SENSOR POWER SUPPLY CIRCUIT
1. Turn ignition switch ªONº.
2. Check voltage between absolute pressure sensor terminal 1 and ground with CONSULT-II or tester.
SEF299X
OK or NG
OK©GO TO 4.
NG©Repair harness or connectors.
4 CHECK ABSOLUTE PRESSURE SENSOR GROUND CIRCUIT FOR OPEN AND SHORT
1. Turn ignition switch ªOFFº.
2. Check harness continuity between absolute pressure sensor terminal 3 and engine ground.
Refer to Wiring Diagram.
Continuity should exist.
3. Also check harness for short to ground and short to power.
OK or NG
OK©GO TO 6.
NG©GO TO 5.
5 DETECT MALFUNCTIONING PART
Check the following.
IHarness for open or short between ECM and absolute pressure sensor
IHarness for open or short between TCM (Transmission Control Module) and absolute pressure sensor
©Repair open circuit or short to ground or short to power in harness or connectors.
6 CHECK ABSOLUTE PRESSURE SENSOR INPUT SIGNAL CIRCUIT FOR OPEN AND SHORT
1. Disconnect ECM harness connector.
2. Check harness continuity between ECM terminal 80 and absolute pressure sensor terminal 2.
Continuity should exist.
3. Also check harness for short to ground and short to power.
OK or NG
OK©GO TO 7.
NG©Repair open circuit or short to ground or short to power in harness or connectors.
DTC P0105 ABSOLUTE PRESSURE SENSOR
Diagnostic Procedure (Cont'd)
EC-162

7 CHECK ABSOLUTE PRESSURE SENSOR
1. Remove absolute pressure sensor with its harness connector connected.
2. Remove hose from absolute pressure sensor.
3. Install a vacuum pump to absolute pressure sensor.
4. Turn ignition switch ªONº and check output voltage between ECM terminal 80 and engine ground under the following
conditions.
SEF300XA
CAUTION:
IAlways calibrate the vacuum pump gauge when using it.
IDo not apply below þ93.3 kPa (±700 mmHg, ±27.56 inHg) or over 101.3 kPa (760 mmHg, 29.92 inHg) of pressure.
OK or NG
OK©GO TO 8.
NG©Replace absolute pressure sensor.
8 CHECK INTERMITTENT INCIDENT
Refer to ªTROUBLE DIAGNOSIS FOR INTERMITTENT INCIDENTº, EC-140.
©INSPECTION END
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DTC P0105 ABSOLUTE PRESSURE SENSOR
Diagnostic Procedure (Cont'd)
EC-163

SEF962Y
SEF012P
Component DescriptionNBEC0064The intake air temperature sensor is mounted to the air duct hous-
ing. The sensor detects intake air temperature and transmits a sig-
nal to the ECM.
The temperature sensing unit uses a thermistor which is sensitive
to the change in temperature. Electrical resistance of the thermistor
decreases in response to the temperature rise.

Intake air
temperature ÉC (ÉF)Voltage* V Resistance kW
20 (68) 3.5 2.1 - 2.9
80 (176) 1.23 0.27 - 0.38
*: These data are reference values and are measured between ECM terminal 64
(Intake air temperature sensor) and body ground.
CAUTION:
Do not use ECM ground terminals when measuring input/
output voltage. Doing so may result in damage to the ECM's
transistor. Use a ground other than ECM terminals, such as
the ground.
On Board Diagnosis LogicNBEC0065Malfunction is detected when
(Malfunction A)an excessively low or high voltage from the sen-
sor is sent to ECM,
(Malfunction B)rationally incorrect voltage from the sensor is sent
to ECM, compared with the voltage signal from engine coolant
temperature sensor.
Possible CauseNBEC0428IHarness or connectors
(The sensor circuit is open or shorted.)
IIntake air temperature sensor
DTC Confirmation ProcedureNBEC0066Perform ªPROCEDURE FOR MALFUNCTION Aº first. If 1st trip
DTC cannot be confirmed, perform ªPROCEDURE FOR MAL-
FUNCTION Bº.
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.
DTC P0110 INTAKE AIR TEMPERATURE SENSOR
Component Description
EC-164

SEF058Y
PROCEDURE FOR MALFUNCTION ANBEC0066S01With CONSULT-IINBEC0066S01011) Turn ignition switch ªONº.
2) Select ªDATA MONITORº mode with CONSULT-II.
3) Wait at least 5 seconds.
4) If 1st trip DTC is detected, go to ªDiagnostic Procedureº,
EC-167.
With GSTNBEC0066S0102Follow the procedure ªWith CONSULT-IIº above.
SEF176Y
PROCEDURE FOR MALFUNCTION BNBEC0066S02CAUTION:
Always drive vehicle at a safe speed.
TESTING CONDITION:
This 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.
With CONSULT-IINBEC0066S02011) Wait until engine coolant temperature is less than 90ÉC
(194ÉF).
a) Turn ignition switch ªONº.
b) Select ªDATA MONITORº mode with CONSULT-II.
c) Check the engine coolant temperature.
d) If the engine coolant temperature is not less than 90ÉC
(194ÉF), turn ignition switch ªOFFº and cool down engine.
IPerform the following steps before engine coolant temperature
is above 90ÉC (194ÉF).
2) Turn ignition switch ªONº.
3) Select ªDATA MONITORº mode with CONSULT-II.
4) Start engine.
5) Hold vehicle speed at more than 70 km/h (43 MPH) for 100
consecutive seconds.
6) If 1st trip DTC is detected, go to ªDiagnostic Procedureº,
EC-167.
With GSTNBEC0066S0202Follow the procedure ªWith CONSULT-IIº above.
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DTC P0110 INTAKE AIR TEMPERATURE SENSOR
DTC Confirmation Procedure (Cont'd)
EC-165