engine INFINITI QX4 2001 Factory Service Manual

DIAGNOSTIC PROCEDURENBEC0049
1 INSPECTION START
Start engine.
Is engine running?
YesorNo
Ye s©GO TO 9.
No©GO TO 2.
2 CHECK ECM POWER SUPPLY CIRCUIT-I
1. Turn ignition switch ªOFFº and then ªONº.
2. Check voltage between ECM terminal 43 and ground with CONSULT-II or tester.
SEF291X
OK or NG
OK©GO TO 4.
NG©GO TO 3.
3 DETECT MALFUNCTIONING PART
Check the following.
I10A fuses
IHarness connectors M33, F22
IHarness for open or short between ECM and ignition switch
©Repair harness or connectors.
4 CHECK ECM GROUND CIRCUIT FOR OPEN AND SHORT-I
1. Turn ignition switch ªOFFº.
2. Disconnect ECM harness connector.
3. Check harness continuity between ECM terminals 48, 57, 106, 108 and engine ground.
Refer to WIRING DIAGRAM.
Continuity should exist.
4. Also check harness for short to ground and short to power.
OK or NG
OK©GO TO 5.
NG©Repair open circuit or short to ground or short to power in harness or connectors.
TROUBLE DIAGNOSIS FOR POWER SUPPLY
Main Power Supply and Ground Circuit (Cont'd)
EC-144

9 CHECK ECM POWER SUPPLY CIRCUIT-II
1. Stop engine.
2. Check voltage between ECM terminal 67 and ground with CONSULT-II or tester.
SEF293X
OK or NG
OK©GO TO 11.
NG©GO TO 10.
10 DETECT MALFUNCTIONING PART
Check the following.
IHarness connectors E1, M1 and M32, F23
IHarness for open or short between ECM and fuse
©Repair harness or connectors.
11 CHECK ECM POWER SUPPLY CIRCUIT-III
1. Turn ignition switch ªONº and then ªOFFº.
2. Check voltage between ECM terminals 110, 112 and ground with CONSULT-II or tester.
SEF294X
OK or NG
OK©GO TO 17.
NG (Battery voltage
does not exist.)©GO TO 12.
NG (Battery voltage
exists for more than a
few seconds.)©GO TO 14.
TROUBLE DIAGNOSIS FOR POWER SUPPLY
Main Power Supply and Ground Circuit (Cont'd)
EC-146

15 DETECT MALFUNCTIONING PART
Check the following.
IHarness connectors E1, M1
IHarness connectors M94, F27
I10A fuse
©Repair harness or connectors.
16 CHECK HARNESS CONTINUITY BETWEEN ECM RELAY AND ECM FOR OPEN AND SHORT
1. Check harness continuity between ECM terminals 110, 112 and ECM relay terminal 6.
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 18.
NG©GO TO 17.
17 DETECT MALFUNCTIONING PART
Check the following.
IHarness connectors E1, M1 and M32, F23
IHarness for open or short between ECM and ECM relay
©Repair open circuit or short to ground or short to power in harness or connectors.
18 CHECK ECM RELAY
1. Apply 12V direct current between ECM relay terminals 1 and 2.
2. Check continuity between relay terminals 3 and 5, 6 and 7.
SEF296X
OK or NG
OK©GO TO 19.
NG©Replace ECM relay.
19 CHECK ECM GROUND CIRCUIT FOR OPEN AND SHORT-II
1. Turn ignition switch ªOFFº.
2. Disconnect ECM harness connector.
3. Check harness continuity between ECM terminals 48, 57, 106, 108 and engine ground.
Refer to WIRING DIAGRAM.
Continuity should exist.
4. Also check harness for short to ground and short to power.
OK or NG
OK©GO TO 20.
NG©Repair open circuit or short to ground or short to power in harness or connectors.
TROUBLE DIAGNOSIS FOR POWER SUPPLY
Main Power Supply and Ground Circuit (Cont'd)
EC-148

SEF958Y
Component DescriptionNBEC0050The mass air flow sensor is placed in the stream of intake air. It
measures the intake flow rate by measuring a part of the entire
intake flow. It consists of a hot film that is supplied with electric
current from the ECM. The temperature of the hot film is controlled
by the ECM a certain amount. The heat generated by the hot film
is reduced as the intake air flows around it. The more air, the
greater the heat loss.
Therefore, the ECM must supply more electric current to maintain
the temperature of the hot film as air flow increases. The ECM
detects the air flow by means of this current change.
CONSULT-II Reference Value in Data Monitor
Mode
NBEC0051Specification data are reference values.
MONITOR ITEM CONDITION SPECIFICATION
MAS A/F SE-B1IEngine: After warming up
IAir conditioner switch: ªOFFº
IShift lever: ªNº
INo-loadIdle 1.2 - 1.8V
2,500 rpm 1.6 - 2.2V
CAL/LD VALUE dittoIdle 14.0 - 33.0%
2,500 rpm 12.0 - 25.0%
MASS AIRFLOW dittoIdle 2.0 - 6.0 g´m/s
2,500 rpm 7.0 - 20.0 g´m/s
ECM Terminals and Reference ValueNBEC0649Specification 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)
61 OR Mass air flow sensor[Engine is running]
IWarm-up condition
IIdle speed1.2 - 1.8V
[Engine is running]
IWarm-up condition
IEngine speed is 2,500 rpm.1.6 - 2.2V
73 B/PMass air flow sensor
ground[Engine is running]
IWarm-up condition
IIdle speedApproximately 0V
111 P/B Sensors' power supply[Ignition switch ªONº]Approximately 5V
DTC P0100 MASS AIR FLOW SENSOR (MAFS)
Component Description
EC-150

On Board Diagnosis LogicNBEC0053Malfunction 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 MODENBEC0053S02When 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 CauseNBEC0426MALFUNCTION A OR CNBEC0426S01IHarness or connectors
(The sensor circuit is open or shorted.)
IMass air flow sensor
MALFUNCTION B, D OR ENBEC0426S02IHarness or connectors
(The sensor circuit is open or shorted.)
IIntake air leaks
IMass air flow sensor
DTC Confirmation ProcedureNBEC0054Perform ªPROCEDURE FOR MALFUNCTION Aº first.
If the 1st trip DTC cannot be confirmed, perform ªPROCE-
DURE FOR MALFUNCTION B AND Eº.
If there is no problem on ªPROCEDURE FOR MALFUNCTION
B AND Eº, perform ªPROCEDURE FOR MALFUNCTION Cº.
If there is no problem on ªPROCEDURE FOR MALFUNCTION
Cº, perform ªPROCEDURE FOR MALFUNCTION Dº.
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.
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DTC P0100 MASS AIR FLOW SENSOR (MAFS)
On Board Diagnosis Logic
EC-151

SEF058Y
PROCEDURE FOR MALFUNCTION ANBEC0054S01With CONSULT-IINBEC0054S01011) Turn ignition switch ªONº.
2) Select ªDATA MONITORº mode with CONSULT-II.
3) Wait at least 6 seconds.
4) If 1st trip DTC is detected, go to ªDiagnostic Procedureº,
EC-155.
With GSTNBEC0054S0102Follow the procedure ªWith CONSULT-IIº above.
SEF058Y
PROCEDURE FOR MALFUNCTION B AND ENBEC0054S02With CONSULT-IINBEC0054S02011) Turn ignition switch ªONº.
2) Select ªDATA MONITORº mode with CONSULT-II.
3) Start engine and wait 5 seconds at most.
4) If 1st trip DTC is detected, go to ªDiagnostic Procedureº,
EC-155.
With GSTNBEC0054S0202Follow the procedure ªWith CONSULT-IIº above.
NOTE:
If 1st trip DTC is confirmed after more than 5 seconds, there may
be malfunction C.
SEF174Y
PROCEDURE FOR MALFUNCTION CNBEC0054S03NOTE:
If engine will not start or stops soon, wait at least 10 seconds with
engine stopped (Ignition switch ªONº) instead of running engine at
idle speed.
With CONSULT-IINBEC0054S03011) Turn ignition switch ªONº.
2) Select ªDATA MONITORº 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 ªDiagnostic Procedureº,
EC-155.
With GSTNBEC0054S0302Follow the procedure ªWith CONSULT-IIº above.
DTC P0100 MASS AIR FLOW SENSOR (MAFS)
DTC Confirmation Procedure (Cont'd)
EC-152

SEF243Y
SEF175Y
PROCEDURE FOR MALFUNCTION DNBEC0054S04CAUTION:
Always drive vehicle at a safe speed.
With CONSULT-IINBEC0054S04021) Turn ignition switch ªONº.
2) Start engine and warm it up to normal operating temperature.
If engine cannot be started, go to ªDiagnostic Procedureº,
EC-155.
3) Select ªDATA MONITORº mode with CONSULT-II.
4) Check the voltage of MAS AIR/FL SE with ªDATA MONITORº.
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 ªDiagnostic Procedureº, 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 ªDiagnostic Procedureº,
EC-155.
SEF534P
Overall Function CheckNBEC0055PROCEDURE FOR MALFUNCTION DNBEC0055S01Use 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 GSTNBEC0055S01011) Start engine and warm it up to normal operating temperature.
2) Select ªMODE 1º with GST.
3) Check the mass air flow sensor signal with ªMODE 1º.
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 ªDiagnostic Procedureº, EC-155.
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DTC P0100 MASS AIR FLOW SENSOR (MAFS)
DTC Confirmation Procedure (Cont'd)
EC-153

Diagnostic ProcedureNBEC0057
1 INSPECTION START
Which malfunction (A, B, C, D or E) is duplicated?
MTBL0373
Type I or Type II
Type I©GO TO 3.
Type II©GO TO 2.
2 CHECK INTAKE SYSTEM
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 3.
NG©Reconnect the parts.
3 RETIGHTEN GROUND SCREWS
1. Turn ignition switch ªOFFº.
2. Loosen and retighten engine ground screws.
SEF959Y
©GO TO 4.
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DTC P0100 MASS AIR FLOW SENSOR (MAFS)
Diagnostic Procedure
EC-155

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