2001 INFINITI QX4 air condition

Basic InspectionNBEC0038Precaution:
Perform Basic Inspection without electrical or mechanical
loads applied;
IHeadlamp switch is OFF,
IAir conditioner switch is OFF,
IRear window defogger switch is OFF,
ISteering wheel is in the straight-ahead position, etc.
1 INSPECTION START
1. Check service records for any recent repairs that may indicate a related problem, or a current need for scheduled
maintenance.
2. Open engine hood and check the following:
IHarness connectors for improper connections
IVacuum hoses for splits, kinks and improper connections
IWiring for improper connections, pinches and cuts
IAir cleaner clogging
IHoses and ducts for leaks
SEF983U
©GO TO 2.
2 CHECK THROTTLE OPENER OPERATION-I
Confirm that there is a clearance between throttle drum and stopper.
SEF950Y
OK or NG
OK©GO TO 4.
NG©GO TO 3.
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TROUBLE DIAGNOSIS Ð BASIC INSPECTION
Basic Inspection
EC-101

Fail-safe Chart=NBEC0040The ECM enters fail-safe mode, if any of the following malfunctions is detected due to the open or short cir-
cuit. When the ECM enters the fail-safe mode, the MIL illuminates.
DTC No. Detected items Engine operating condition in fail-safe mode
P0100 Mass air flow sensor circuit Engine speed will not rise more than 2,400 rpm due to the fuel cut.
P0115 Engine coolant temperature
sensor circuitEngine coolant temperature will be determined by ECM based on the time after
turning ignition switch ªONº or ªSTARTº.
CONSULT-II displays the engine coolant temperature decided by ECM.
ConditionEngine coolant temperature decided
(CONSULT-II display)
Just as ignition switch is turned
ON or Start40ÉC (104ÉF)
More than approx. 4 minutes
after ignition ON or Start80ÉC (176ÉF)
Except as shown above40 - 80ÉC (104 - 176ÉF)
(Depends on the time)
P0120 Throttle position sensor cir-
cuitThrottle position will be determined based on the injected fuel amount and the
engine speed.
Therefore, acceleration will be poor.
Condition Driving condition
When engine is idling Normal
When accelerating Poor acceleration
P1335 Crankshaft position sensor
(REF) circuitCompression TDC signal (120É signal) is controlled by camshaft position sensor
(PHASE) signal and crankshaft position sensor (POS) signal. Ignition timing will be
delayed 0É to 2É.
Unable to
access ECMECMECM fail-safe activating condition
The computing function of the ECM was judged to be malfunctioning.
When the fail-safe system activates (i.e., if the ECM detects a malfunction condi-
tion in the CPU of ECM), the MIL on the instrument panel lights to warn the driver.
However it is not possible to access ECM and DTC cannot be confirmed.
Engine control with fail-safe
When ECM fail-safe is operating, fuel injection, ignition timing, fuel pump operation,
IACV-AAC valve operation and cooling fan operation are controlled under certain
limitations.
ECM fail-safe operation
Engine speedEngine speed will not rise more than 3,000
rpm
Fuel injection Simultaneous multiport fuel injection system
Ignition timing Ignition timing is fixed at the preset valve
Fuel pumpFuel pump relay is ªONº when engine is running
and ªOFFº when engine stalls
IACV-AAC valve Full open
Replace ECM, if ECM fail-safe condition is confirmed.
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TROUBLE DIAGNOSIS Ð GENERAL DESCRIPTION
Fail-safe Chart
EC-117

Symptom Matrix ChartNBEC0041SYSTEM Ð BASIC ENGINE CONTROL SYSTEMNBEC0041S01
SYMPTOM
Reference
page
HARD/NO START/RESTART (EXCP. HA)
ENGINE STALL
HESITATION/SURGING/FLAT SPOT
SPARK KNOCK/DETONATION
LACK OF POWER/POOR ACCELERATION
HIGH IDLE/LOW IDLE
ROUGH IDLE/HUNTING
IDLING VIBRATION
SLOW/NO RETURN TO IDLE
OVERHEATS/WATER TEMPERATURE HIGH
EXCESSIVE FUEL CONSUMPTION
EXCESSIVE OIL CONSUMPTION
BATTERY DEAD (UNDER CHARGE)
Warranty symptom code AA AB AC AD AE AF AG AH AJ AK AL AM HA
Fuel Fuel pump circuit11232 2 2 3 2EC-625
Fuel pressure regulator system3344444 4 4 4EC-40
Injector circuit11232 2 2 2EC-616
Evaporative emission system
3344444 4 4 4EC-32
Air Positive crankcase ventilation sys-
tem1 EC-38
Incorrect idle speed adjustment 1 1 1 1 1 EC-101
IACV-AAC valve circuit1123322 2 2 2 2EC-422
Ignition Incorrect ignition timing adjustment33111 1 1 1EC-101
Ignition circuit 1 1 2 2 2 2 2 2 EC-499
Main power supply and ground circuit
22333 3 32
3EC-142
Air conditioner circuit 3 3 2 HA section
1 - 6: The numbers refer to the order of inspection.
(continued on next page)
TROUBLE DIAGNOSIS Ð GENERAL DESCRIPTION
Symptom Matrix Chart
EC-118

SYMPTOM
Reference
section
HARD/NO START/RESTART (EXCP. HA)
ENGINE STALL
HESITATION/SURGING/FLAT SPOT
SPARK KNOCK/DETONATION
LACK OF POWER/POOR ACCELERATION
HIGH IDLE/LOW IDLE
ROUGH IDLE/HUNTING
IDLING VIBRATION
SLOW/NO RETURN TO IDLE
OVERHEATS/WATER TEMPERATURE HIGH
EXCESSIVE FUEL CONSUMPTION
EXCESSIVE OIL CONSUMPTION
BATTERY DEAD (UNDER CHARGE)
Warranty symptom code AA AB AC AD AE AF AG AH AJ AK AL AM HA
IVIS (INFINITI Vehicle Immobilizer System Ð
NATS)11EC-74 or EL
section
1 - 6: The numbers refer to the order of inspection.
CONSULT-II Reference Value in Data Monitor
Mode
NBEC0042Remarks:
ISpecification data are reference values.
ISpecification data are output/input values which are detected or supplied by the ECM at the connector.
* Specification data may not be directly related to their components signals/values/operations.
i.e. Adjust ignition timing with a timing light before monitoring IGN TIMING, because the monitor may show the specification data in
spite of the ignition timing not being adjusted to the specification data. This IGN TIMING monitors the data calculated by the ECM
according to the signals input from the camshaft position sensor and other ignition timing related sensors.
IIf the real-time diagnosis results are NG and the on board diagnostic system results are OK when diagnosing the mass air flow sensor,
first check to see if the fuel pump control circuit is normal.
MONITOR ITEM CONDITION SPECIFICATION
ENG SPEED
CKPS´RPM (POS)ITachometer: Connect
IRun engine and compare tachometer indication with the CONSULT-II
value.Almost the same speed as
the CONSULT-II value.
POS COUNTIEngine: Running 179 - 181
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
COOLAN TEMP/SIEngine: After warming up More than 70ÉC (158ÉF)
HO2S1 (B1)
HO2S1 (B2)
IEngine: After warming upMaintaining engine speed at 2,000
rpm0 - 0.3V+,Approx. 0.6 -
1.0V
HO2S1 MNTR (B1)
HO2S1 MNTR (B2)LEAN+,RICH
Changes more than 5 times
during 10 seconds.
HO2S2 (B1)
HO2S2 (B2)
IEngine: After warming upMaintaining engine speed at 2,000
rpm0 - 0.3V+,Approx. 0.6 -
1.0V
HO2S2 MNTR (B1)
HO2S2 MNTR (B2)LEAN+,RICH
TROUBLE DIAGNOSIS Ð GENERAL DESCRIPTION
Symptom Matrix Chart (Cont'd)
EC-122

MONITOR ITEM CONDITION SPECIFICATION
VHCL SPEED SEITurn drive wheels and compare speedometer indication with the CON-
SULT-II valueAlmost the same speed as
the CONSULT-II value
BATTERY VOLTIIgnition switch: ON (Engine stopped) 11 - 14V
THRTL POS SENIEngine: After warming up, idle
the engineThrottle valve: fully closed 0.15 - 0.85V
IEngine: After warming up
IIgnition switch: ON
(Engine stopped)Throttle valve: fully opened 3.5 - 4.7V
START SIGNALIIgnition switch: ON,START,ON OFF,ON,OFF
CLSD THL POS
CLSD THL/P SWIEngine: After warming up, idle
the engineThrottle valve: Idle position ON
Throttle valve: Slightly open OFF
AIR COND SIGIEngine: After warming up, idle
the engineAir conditioner switch: ªOFFº OFF
Air conditioner switch: ªONº
(Compressor operates.)ON
P/N POSI SWIIgnition switch: ONShift lever: ªPº or ªNº ON
Except above OFF
PW/ST SIGNALIEngine: After warming up, idle
the engineSteering wheel in neutral position
(forward direction)OFF
The steering wheel is turned ON
IGNITION SWIIgnition switch: ON,OFF,ON ON,OFF,ON
INJ PULSE-B2
INJ PULSE-B1IEngine: After warming up
IAir conditioner switch: ªOFFº
IShift lever: ªNº
INo-loadIdle 2.4 - 3.2 msec
2,000 rpm 1.9 - 2.8 msec
B/FUEL SCHDLIEngine: After warming up
IAir conditioner switch: ªOFFº
IShift lever: ªNº
INo-loadIdle 2.0 - 3.2 msec
2,000 rpm 1.4 - 2.6 msec
IGN TIMINGIEngine: After warming up
IAir conditioner switch: ªOFFº
IShift lever: ªNº
INo-loadIdle 15ɱ5É BTDC
2,000 rpm More than 25É BTDC
IACV-AAC/VIEngine: After warming up
IAir conditioner switch: ªOFFº
IShift lever: ªNº
INo-loadIdle 2 - 10 step
2,000 rpm Ð
PURG VOL C/VIEngine: After warming up
IAir conditioner switch: ªOFFº
IShift lever: ªNº
INo-loadIdle 0 %
2,000 rpm Ð
A/F ALPHA-B2
A/F ALPHA-B1IEngine: After warming upMaintaining engine speed at 2,000
rpm54 - 155%
EVAP SYS PRESIIgnition switch: ON Approx. 3.4V
AIR COND RLYIAir conditioner switch: OFF,ON OFF,ON
FUEL PUMP RLYIIgnition switch is turned to ON (Operates for 5 seconds)
IEngine running and crankingON
Except as shown above OFF
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TROUBLE DIAGNOSIS Ð GENERAL DESCRIPTION
CONSULT-II Reference Value in Data Monitor Mode (Cont'd)
EC-123

MONITOR ITEM CONDITION SPECIFICATION
VENT CONT/VIIgnition switch: ON OFF
HO2S1 HTR (B1)
HO2S1 HTR (B2)IEngine speed: Below 3,600 rpm ON
IEngine speed: Above 3,600 rpm OFF
HO2S2 HTR (B1)
HO2S2 HTR (B2)IIgnition switch: ON (Engine stopped)
IEngine speed: Above 3,200 rpmOFF
IEngine speed: Below 3,200 rpm [After driving for 2 minutes at a speed
of 70 km/h (43 MPH) or more]ON
VC/V BYPASS/V Ignition switch: ON OFF
CAL/LD VALUEIEngine: After warming up
IAir conditioner switch: ªOFFº
IShift lever: ªNº
INo-loadIdle 14.0 - 33.0%
2,500 rpm 12.0 - 25.0%
ABSOL TH´P/SIEngine: After warming up Throttle valve: fully closed 0.0%
IEngine: After warming up
IIgnition switch: ON
(Engine stopped)Throttle valve: fully opened Approx. 80%
MASS AIRFLOWIEngine: After warming up
IAir conditioner switch: ªOFFº
IShift lever: ªNº
INo-loadIdle 2.0 - 6.0 g´m/s
2,500 rpm 7.0 - 20.0 g´m/s
ABSOL PRES/SEIIgnition switch: ON Approx. 4.4V
SWRL CONT S/VIEngine speed: IdleEngine coolant temperature is
between 15ÉC (59ÉF) to 50ÉC
(122ÉF).ON
Engine coolant temperature is above
55ÉC (131ÉF).OFF
SWL CON VC SWIEngine speed: Idle
IEngine coolant temperature is between 15ÉC (59ÉF) to 50ÉC (122ÉF).OFF
IEngine speed: Idle
IEngine coolant temperature is above 55ÉC (131ÉF).ON
INT/V TIM (B1)
INT/V TIM (B2)IEngine: After warming up
IShift lever ªNº
IQuickly depressed accelerator
pedal
INo-loadIdle 0É CA
2,000 rpm Approximately 12 - 18É CA
INT/V SOL (B1)
INT/V SOL (B2)IEngine: After warming up
IShift lever ªNº
IQuickly depressed accelerator
pedal
INo-loadIdle 0%
2,000 rpm Approximately 40%
Major Sensor Reference Graph in Data Monitor
Mode
NBEC0043The following are the major sensor reference graphs in ªDATA MONITORº mode.
THRTL POS SEN, ABSOL TH´P/S, CLSD THL POSNBEC0043S01Below is the data for ªTHRTL POS SENº, ªABSOL TH´P/Sº and ªCLSD THL POSº when depressing the accel-
erator pedal with the ignition switch ªONº.
The signal of ªTHRTL POS SENº and ªABSOL TH´P/Sº should rise gradually without any intermittent drop or
rise after ªCLSD THL POSº is changed from ªONº to ªOFFº.
TROUBLE DIAGNOSIS Ð GENERAL DESCRIPTION
CONSULT-II Reference Value in Data Monitor Mode (Cont'd)
EC-124

TERMI-
NAL
NO.WIRE
COLORITEM CONDITION DATA (DC Voltage)
25 W/G Tachometer[Engine is running]
IWarm-up condition
IIdle speed7-8VH
SEF579X
[Engine is running]
IWarm-up condition
IEngine speed is 2,500 rpm.7-8VH
SEF580X
26 L/BECM relay
(Self shutt-off)[Engine is running]
[Ignition switch ªOFFº]
IFor a few seconds after turning ignition switch
ªOFFº0 - 1.5V
[Ignition switch ªOFFº]
IA few seconds passed after turning ignition
switch ªOFFºBATTERY VOLTAGE
(11 - 14V)
27 LG Air conditioner relay[Engine is running]
IBoth A/C switch and blower switch are ªONº
(Compressor is operating).0 - 1.0V
[Engine is running]
IA/C switch is ªOFFº.BATTERY VOLTAGE
(11 - 14V)
28 R/L Fuel pump relay[Ignition switch ªONº]
IFor 1 second after turning ignition switch ªONº
[Engine is running]0 - 1.5V
[Ignition switch ªONº]
I1 second passed after turning ignition switch
ªONº.BATTERY VOLTAGE
(11 - 14V)
29 GSwirl control valve con-
trol solenoid valve[Engine is running]
IIdle speed
IEngine coolant temperature is between 15 to
50ÉC (59 to 122ÉF).0 - 1.0V
[Engine is running]
IIdle speed
IEngine coolant temperature is above 55ÉC
(131ÉF).BATTERY VOLTAGE
(11 - 14V)
38 OR MIL[Ignition switch ªONº]0 - 1.0V
[Engine is running]
IIdle speedBATTERY VOLTAGE
(11 - 14V)
39 G/WVacuum cut valve
bypass valve[Ignition switch ªONº]BATTERY VOLTAGE
(11 - 14V)
40 G/YEVAP canister vent
control valve[Ignition switch ªONº]BATTERY VOLTAGE
(11 - 14V)
TROUBLE DIAGNOSIS Ð GENERAL DESCRIPTION
ECM Terminals and Reference Value (Cont'd)
EC-130

TERMI-
NAL
NO.WIRE
COLORITEM CONDITION DATA (DC Voltage)
42 B/Y Start signal[Ignition switch ªONº]Approximately 0V
[Ignition switch ªSTARTº]9 - 12V
43 R Ignition switch[Ignition switch ªOFFº]0V
[Ignition switch ªONº]BATTERY VOLTAGE
(11 - 14V)
44 L PNP switch[Ignition switch ªONº]
IGear position is ªPº or ªNº.Approximately 0V
[Ignition switch ªONº]
IExcept the above gear positionBATTERY VOLTAGE
(11 - 14V)
45 B/RAir conditioner switch
signal[Engine is running]
IBoth A/C switch and blower switch are ªONº.Approximately 0V
[Engine is running]
IA/C switch is ªOFFº.Approximately 5V
47 R/BPower steering oil
pressure switch[Engine is running]
ISteering wheel is being turned.0 - 1.0V
[Engine is running]
ISteering wheel is not being turned.Approximately 5V
48 B ECM ground[Engine is running]
IIdle speedEngine ground
51 BR A/C cut signal[Engine is running]
IAir conditioner is operating.0 - 0.5V
52 PU Electrical load signal[Engine is running]
IRear window defogger: ON
IHi-beam headlamp: ONBATTERY VOLTAGE
(11 - 14V)
[Engine is running]
IElectrical load: OFF0V
55 W/BSwirl control valve con-
trol vacuum check
switch[Engine is running]
IIdle speed
IEngine coolant temperature is between 15 to
50ÉC (59 to 122ÉF).Approximately 5V
[Engine is running]
IIdle speed
IEngine coolant temperature is above 55ÉC
(131ÉF).0 - 1.0V
56 OR/LThrottle position switch
(Closed position)[Engine is running]
IAccelerator pedal fully releasedBATTERY VOLTAGE
(11 - 14V)
[Engine is running]
IAccelerator pedal depressedApproximately 0V
57 B ECM ground[Engine is running]
IIdle speedEngine ground
58 B/P Sensors' ground[Engine is running]
IWarm-up condition
IIdle speedApproximately 0V
59 BFuel level sensor
ground[Engine is running]
IIdle speedApproximately 0V
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TROUBLE DIAGNOSIS Ð GENERAL DESCRIPTION
ECM Terminals and Reference Value (Cont'd)
EC-131