2001 INFINITI QX4 cooling

DescriptionNBEC0249SYSTEM DESCRIPTIONNBEC0249S01
Sensor Input Signal to ECMECM func-
tionActuator
Crankshaft position sensor (POS) Engine speed (POS signal)
Idle air
controlIACV-AAC valve Crankshaft position sensor (REF) Engine speed (REF signal)
Mass air flow sensor Amount of intake air
Engine coolant temperature sensor Engine coolant temperature
Ignition switch Start signal
Throttle position sensor Throttle position
Park/neutral position (PNP) switch Park/neutral position
Air conditioner switch Air conditioner operation
Power steering oil pressure switch Power steering load signal
Battery Battery voltage
Vehicle speed sensor Vehicle speed
Ambient air temperature switch Ambient air temperature
Intake air temperature sensor Intake air temperature
Absolute pressure sensor Ambient barometic pressure
This system automatically controls engine idle speed to a specified
level. Idle speed is controlled through fine adjustment of the
amount of air which by-passes the throttle valve via IACV-AAC
valve. The IACV-AAC valve changes the opening of the air by-pass
passage to control the amount of auxiliary air. This valve is actu-
ated by a step motor built into the valve, which moves the valve in
the axial direction in steps corresponding to the ECM output sig-
nals. One step of IACV-AAC valve movement causes the respec-
tive opening of the air by-pass passage. (i.e. when the step
advances, the opening is enlarged.) The opening of the valve is
varied to allow for optimum control of the engine idling speed. The
crankshaft position sensor (POS) detects the actual engine speed
and sends a signal to the ECM. The ECM then controls the step
position of the IACV-AAC valve so that engine speed coincides with
the target value memorized in ECM. The target engine speed is the
lowest speed at which the engine can operate steadily. The opti-
mum value stored in the ECM is determined by takig into consid-
eration various engine conditions, such as during warm up,
deceleration, and engine load (air conditioner, power steering and
cooling fan operation).
SEF765P
COMPONENT DESCRIPTIONNBEC0249S02IACV-AAC ValveNBEC0249S0201The IACV-AAC valve is operated by a step motor for centralized
control of auxiliary air supply. This motor has four winding phases
and is actuated by the output signals of ECM which turns ON and
OFF two windings each in seqeunce. Each time the IACV-AAC
valve opens or closes to change tha auxiliary air quantity, the ECM
sends a pulse signal to the step motor. When no change in the
auxiliary air quantity is needed, the ECM does not issue the pulse
signal. A certain voltage signal is issued so that the valve remains
at that particular opening.
DTC P0505 IDLE AIR CONTROL VALVE (IACV) Ð AUXILIARY AIR CONTROL
(AAC) VALVE
Description
EC-422

SEF029Z
DescriptionNBEC0636The refrigerant pressure sensor is installed at the liquid tank of the
air conditioner system. The sensor uses an electrostatic volume
pressure transducer to convert refrigerant pressure to voltage. The
voltage signal is sent to ECM, and ECM controls cooling fan sys-
tem.
SEF099XA
ECM Terminals and Reference ValueNBEC0689Specification 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)
58 B/P Sensors' ground[Engine is running]
IWarm-up condition
IIdle speedApproximately 0V
81 W/PURefrigerant pressure
sensor[Engine is running]
IWarm-up condition
IBoth A/C switch and blower switch are ªONº.
(Compressor operates.)1.0 - 4.0V
111 P/B Sensors' power supply[Ignition switch ªONº]Approximately 5V
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REFRIGERANT PRESSURE SENSOR
Description
EC-639

System DescriptionNBEL0153
SEL713U
This unit displays following items:
IEarth magnetism and heading direction of vehicle.
IOutside air temperature.
ICaution for frozen road surfaces.
OUTSIDE TEMPERATURE DISPLAYNBEL0153S01Push the switch when the ignition key is in the ªACCº or ªONº position. The outside temperature will be dis-
played in ªÉFº.
ISelecting the indication range
Push the switch to change from ªÉFº to ªÉCº.
IWhen the outside temperature drops below freezing point, ICE is displayed on the unit.
IWhen the outside temperature is between 55ÉC (130ÉF) and 70ÉC (158ÉF), the display shows 55ÉC
(130ÉF).
IWhen the outside temperature is lower than þ30ÉC (þ20ÉF) or higher than 70ÉC (158ÉF), the display shows
only ª---º though it is operating. This is not a problem.
IThe indicated temperature on the thermometer is not readily affected by engine heat. It changes only when
one of the following conditions is present.
a) The temperature detected by the ambient air temperature sensor is lower than the indicated temperature
on the thermometer.
b) The difference in temperature detected during a period of 40 seconds is less than 1ÉC (1.8ÉF) when vehicle
speed has been greater than 24 km/h (15 MPH) for more than 100 seconds.
(This is to prevent the indicated temperature from being affected by engine heat or cooling fan operation
during low-speed driving.)
c) The ignition key has been turned to the ªOFFº position for more than 4 hours. (The engine is cold.)
DIRECTION DISPLAYNBEL0153S02Push the switch when the ignition key is in the ªACCº or ªONº position. The direction will be displayed.
COMPASS AND THERMOMETER
System Description
EL-110

Trouble DiagnosesNBEL0048PRELIMINARY CHECK FOR THERMOMETERNBEL0048S02
1 COOL DOWN CHECK
1. Turn the ignition key switch to the ªACCº position.
2. Cool down the ambient air temperature sensor with water or ice, so that the indicated temperature falls.
Does the indicated temperature fall?
Ye s©GO TO 2.
No©The system is malfunctioning. Check the system following ªINSPECTION/COMPASS
AND THERMOMETERº.
2 WARM UP CHECK
1. Leave the vehicle for 10 minutes, so that the indicated temperature rises.
2. With the ignition key in the ªACCº position, disconnect and reconnect the ambient air temperature sensor connector.
Does the indicated temperature rise?
Ye s©The system is OK.
No©The system is malfunctioning. Check the system following ªINSPECTION/COMPASS
AND THERMOMETERº.
NOTE:
IWhen the outside temperature is between 55ÉC (130ÉF) and 70ÉC (158ÉF), the display shows 55ÉC
(130ÉF). When the outside temperature is lower than þ30ÉC (þ20ÉF) or higher than 70ÉC (158ÉF), the dis-
play shows only ª---º.
IThe indicated temperature on the thermometer is not readily affected by engine heat. It changes only when
one of the following conditions is present.
a) The temperature detected by the ambient air temperature sensor is lower than the indicated temperature
on the thermometer.
b) The difference in temperature detected during a period of 40 seconds is less than 1ÉC (1.8ÉF) when vehicle
speed has been greater than 24 km/h (15 MPH) for more than 100 seconds.
(This is to prevent the indicated temperature from being affected by engine heat or cooling fan operation
during low-speed driving.)
c) The ignition key has been turned to the ªOFFº position for more than 4 hours. (The engine is cold.)
INSPECTION/COMPASS AND THERMOMETERNBEL0048S01
Symptom Possible causes Repair order
No display at all 1. 10A fuse
2. Ground circuit
3. Compass and thermometer1. Check 10A fuse [No. 9, located in fuse block (J/B)].
Turn the ignition switch ON and verify that battery positive
voltage is at terminal 7 of compass and thermometer.
2. Check ground circuit for compass and thermometer.
3. Replace compass and thermometer.
Forward direction indi-
cation slips off the
mark or incorrect.1. In manual correction mode (Bar
and display vanish.)
2. Zone variation change is not done.1. Drive the vehicle and turn at an angle of 90É.
2. Perform the zone variation change.
Compass reading
remains unchanged.1. Vehicle speed sensor is not
entered.
2. Compass and thermometer1. Check harness for open or short between combination meter
terminal 13 and compass and thermometer terminal 1.
2. Replace compass and thermometer.
Displays wrong tem-
perature when ambient
temperature is between
þ30ÉC (þ20ÉF) and
55ÉC (130ÉF). (See
NOTE above.)1. Check operation
2. Ambient air temperature sensor
circuit
3. Vehicle speed sensor is not
entered.
4. Ambient air temperature sensor
5. Compass and thermometer1. Perform preliminary check shown above.
2. Check harness for open or short between ambient air tem-
perature sensor and compass and thermometer.
3. Check harness for open or short between combination meter
terminal 13 and compass and thermometer terminal 1.
4. Replace ambient air temperature sensor.
5. Replace compass and thermometer.
COMPASS AND THERMOMETER
Trouble Diagnoses
EL-112

NVH Troubleshooting Ð Engine NoiseNBEM0005S01Use the chart below to help you find the cause of the symptom.
1. Locate the area where noise occurs.
2. Confirm the type of noise.
3. Specify the operating condition of engine.
4. Check specified noise source.
If necessary, repair or replace these parts.
Location of
noiseType of
noiseOperating condition of engine
Source of
noiseCheck itemReference
page Before
warm-upAfter
warm-upWhen
startingWhen
idlingWhen
racingWhile
driving
To p o f
engine
Rocker
cover
Cylinder
headTicking or
clickingC A ÐA BÐTappet
noiseValve clearance EM-54
Rattle C A Ð A B CCamshaft
bearing
noiseCamshaft journal clear-
ance
Camshaft runoutEM-42, 42
Crankshaft
pulley
Cylinder
block
(Side of
engine)
Oil panSlap or
knockÐ A ÐB BÐPiston pin
noisePiston and piston pin
clearance
Connecting rod bush-
ing clearanceEM-63, 70
Slap or
rapA ÐÐBBAPiston slap
noisePiston-to-bore clear-
ance
Piston ring side clear-
ance
Piston ring end gap
Connecting rod bend
and torsionEM-64, 64,
65, 66
Knock A B C B B BConnect-
ing rod
bearing
noiseConnecting rod bush-
ing clearance (Small
end)
Connecting rod bearing
clearance (Big end)EM-70, 69
Knock A B Ð A B CMain bear-
ing noiseMain bearing oil clear-
ance
Crankshaft runoutEM-67, 67
Front of
engine
Timing
chain
coverTapping or
tickingA A ÐBBBTiming
chain and
chain ten-
sioner
noiseTiming chain cracks
and wear
Timing chain tensioner
operationEM-29, 20
Front of
engineSqueaking
or fizzingA B ÐBÐCOther
drive belts
(Sticking
or slipping)Drive belts deflectionMA section
(ªChecking
Drive
Beltsº,
ªENGINE
MAINTE-
NANCEº) Creaking A BABABOther
drive belts
(Slipping)Idler pulley bearing
operation
Squall
CreakA B ÐBABWater
pump
noiseWater pump operationLC section
(ªWater
Pump
Inspectionº,
ªENGINE
COOLING
SYSTEMº)
A: Closely related B: Related C: Sometimes related Ð: Not related
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NOISE, VIBRATION AND HARSHNESS (NVH) TROUBLESHOOTING
NVH Troubleshooting Ð Engine Noise
EM-9

ComponentsNBEM0008
SEM583G
RemovalNBEM0009WARNING:
IPlace vehicle on a flat and solid surface.
IYou should not remove oil pan until exhaust system and
cooling system have completely cooled off.
Otherwise, you may burn yourself and/or fire may break
out in the fuel line.
IWhen removing front engine mounting nuts, lift up slightly
engine for safety work.
CAUTION:
When removing the aluminum oil pan from engine, first
remove the crankshaft position sensors (POS and REF) from
the assembly.
Be careful not to damage sensor edges and signal plate teeth.
1. Remove front RH and LH wheels.
2. Remove battery.
3. Remove oil level gauge.
4. Remove engine undercover.
5. Remove suspension member stay.
6. Drain engine coolant from radiator drain plug.
7. Disconnect A/T oil cooler hoses.
8. Drain engine oil.
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OIL PAN
Components
EM-15

CAUTION:
IAfter removing timing chain, do not turn crankshaft and
camshaft separately, or valves will strike piston heads.
IWhen installing camshafts, chain tensioners, oil seals, or
other sliding parts, lubricate contacting surfaces with new
engine oil.
IApply new engine oil to bolt threads and seat surfaces
when installing camshaft sprockets and crankshaft pulley.
IBefore disconnecting fuel hose, release fuel pressure.
Refer to EC-39, ªFuel Pressure Releaseº.
IBe careful not to damage sensor edges.
IDo not spill engine coolant on drive belts.
RemovalNBEM00121. Release fuel pressure.
Refer to EC-39, ªFuel Pressure Releaseº.
2. Remove battery.
3. Remove radiator.
Refer to LC-19, ªREMOVAL AND INSTALLATIONº.
4. Drain engine oil.
5. Remove drive belts and idler pulley with brackets.
6. Remove cooling fan with bracket.
7. Remove engine cover.
8. Remove air duct with air cleaner case, collector, blow-by hose,
vacuum hoses, fuel hoses, water hoses, wires, harnesses,
connectors and so on.
9. Remove the air compressor, and tie it down using rope or the
like to keep it from interfering.
10. Remove the power steering oil pump and reservoir tank. Tie
them down using rope or the like to keep them from interfer-
ing.
11. Remove alternator.
12. Remove the following.
IVacuum gallery
IWater bypass pipe
IBrackets
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TIMING CHAIN
Components (Cont'd)
EM-23

SEM828E
7. Apply engine oil to new valve oil seal and install it with Tool.
SEM715A
OIL SEAL INSTALLATION DIRECTIONNBEM0015S02IInstall new oil seal in the direction shown in the figure.
FRONT OIL SEALNBEM0015S031. Remove the following parts:
IEngine undercover
ISuspension member stay
IDrive belts
ICrankshaft position sensor (REF)
Be careful not to damage sensor edge.
ICrankshaft pulley
IRadiator
ICooling fan
SEM829E
2. Remove front oil seal using a suitable tool.
Be careful not to scratch front cover.
3. Apply engine oil to new oil seal and install it using a suitable
tool.
SEM830E
REAR OIL SEALNBEM0015S041. Remove transmission. Refer to AT-277, ªRemovalº.
2. Remove drive plate.
3. Remove oil pan. Refer to EM-15.
4. Remove rear oil seal retainer.
OIL SEAL
Replacement (Cont'd)
EM-36