2001 INFINITI QX4 Ac system

System DescriptionNBEL0216Refer to Owner's Manual for ASCD operating instructions.
POWER SUPPLY AND GROUNDNBEL0216S01Power is supplied at all times:
Ithrough 10A fuse [No. 14, located in the fuse block (J/B)]
Ito the stop lamp switch terminal 1, and
Ithrough 7.5A fuse (No. 52, located in fuse and fusible link box)
Ito the horn relay terminals 1 and 3.
When ignition switch is in the ON or START position, power is supplied:
Ithrough 7.5A fuse [No. 11, located in the fuse block (J/B)]
Ito ASCD brake switch terminal 1 and
Ito ASCD control unit terminal 5,
Ithrough 10A fuse [No. 18, located in the fuse block (J/B)]
Ito park/neutral position relay terminal 1,
Ithrough 10A fuse [No. 8, located in the fuse block (J/B)]
Ito combination meter terminal 66, and
When park/neutral position switch is in the P or N position, ground is supplied:
Ito park/neutral position relay terminal 2
Ithrough park/neutral position switch and body grounds B55 and B75.
When ASCD main switch is depressed (ON), ground is supplied:
Ito ASCD control unit terminal 9
Ifrom ASCD steering switch terminal 4
Ito ASCD steering switch terminal 5
Ithrough body grounds M4, M66 and M147
then ASCD control unit holds CRUISE condition and illuminates CRUISE indicator.
Ground is supplied:
Ifrom ASCD control unit terminal 15
Ito combination meter terminal 46.
OPERATIONNBEL0216S02Set OperationNBEL0216S0201To activate the ASCD, all following conditions must exist.
IGround supply to ASCD control unit terminal 9 (Main switch is in ON position.)
IPower supply to ASCD control unit terminal 8 (Brake pedal is released and A/T selector lever is in other
than P and N position.)
IVehicle speed is between 40 km/h (25 MPH) and 144 km/h (89 MPH). (Signal from combination meter)
When the SET/COAST switch is depressed, power is supplied:
Ifrom ASCD steering switch terminal 2
Ito ASCD control unit terminal 11.
And then ASCD pump is activated to control throttle wire and ASCD control unit supply ground
Ito combination meter terminals 51 to illuminate SET indicator.
A/T Overdrive Control during Cruise Control DrivingNBEL0216S0202When the vehicle speed is approximately 3 km/h (2 MPH) below set speed, a signal is sent
Ifrom ASCD control unit terminal 10
Ito TCM (transmission control module) terminal 24.
When this occurs, the TCM (transmission control module) cancels overdrive.
After vehicle speed is approximately 1 km/h (1 MPH) below set speed, overdrive is reactivated.
ASCD Shifting ControlNBEL0216S0203During ASCD cruise, ASCD control unit controls A/T shifting to avoid uncomfortable shifting.
This is used to control the signals below.
IThrottle position sensor from ECM
AUTOMATIC SPEED CONTROL DEVICE (ASCD)
System Description
EL-222

IA/T shift solenoid valve A
Coast OperationNBEL0216S0204When the SET/COAST switch is depressed during cruise control driving, ASCD actuator returns the throttle
cable to decrease vehicle set speed until the switch is released. And then ASCD will keep the new set speed.
Accel OperationNBEL0216S0205When the RESUME/ACCEL switch is depressed, power is supplied
Ifrom ASCD steering switch terminal 3
Ito ASCD control unit terminal 24.
If the RESUME/ACCEL switch is depressed during cruise control driving, ASCD actuator pulls the throttle cable
to increase the vehicle speed until the switch is released or vehicle speed is reached to maximum controlled
speed by the system. And then ASCD will keep the new set speed.
Cancel OperationNBEL0216S0206When any of following condition exists, cruise operation will be canceled.
ICANCEL switch is depressed. (Power supply to ASCD control unit terminals 11 and 24)
IBrake pedal is depressed. (Power supply to ASCD control unit terminal 23 from stop lamp switch)
IBrake pedal is depressed or A/T selector lever is shifted to P or N position. (Power supply to ASCD con-
trol unit terminal 8 is interrupted.)
If MAIN switch is turned to OFF during ASCD is activated, all of ASCD operation will be canceled and vehicle
speed memory will be erased.
Resume OperationNBEL0216S0207When the RESUME/ACCEL switch is depressed after cancel operation other than depressing MAIN switch is
performed, vehicle speed will return to last set speed. To resume vehicle set speed, vehicle condition must
meet following conditions.
IBrake pedal is released.
IA/T selector lever is in other than P and N position.
IVehicle speed is between 40 km/h (25 MPH) and 144 km/h (89 MPH).
ASCD PUMP OPERATIONNBEL0216S03The ASCD pump consists of a vacuum motor, an air valve and a release valve. When the ASCD activates,
power is supplied
Ifrom terminal 12 of ASCD control unit
Ito ASCD pump terminal 1.
Ground is supplied to vacuum motor, air valve and release valve from ASCD control unit depending on the
operated condition as shown in the below table.
The pump is connected to ASCD actuator by vacuum hose. When the ASCD pump is activated, the ASCD
pump vacuum the diaphragm of ASCD actuator to control throttle cable.
Air valve (*1) Release valve (*1) Vacuum motorActuator inner pres-
sure
ASCD not operating Open Open Stopped Atmosphere
ASCD operatingReleasing throttle
cableOpen Closed Stopped Vacuum
Holding throttle
positionClosed Closed Stopped Vacuum (*2)
Pulling throttle cable Closed Closed Operated Vacuum
*1: When power and ground is supplied, valve is closed.
*2: Set position held.
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AUTOMATIC SPEED CONTROL DEVICE (ASCD)
System Description (Cont'd)
EL-223

SEL255W
Fail-safe SystemNBEL0217DESCRIPTIONNBEL0217S01When the fail-safe system senses a malfunction, it deactivates
ASCD operation. The SET indicator in the combination meter will
then flash.
MALFUNCTION DETECTION CONDITIONSNBEL0217S02
Detection conditionsASCD operation during malfunc-
tion detection
IASCD steering (RESUME/ACCEL, CANCEL, SET/COAST) switch is stuck.
IVacuum motor ground circuit or power circuit is open or shorted.
IAir valve ground circuit or power circuit is open or shorted.
IRelease valve ground circuit or power circuit is open or shorted.
IVehicle speed sensor is faulty.
IASCD control unit internal circuit is malfunctioning.IASCD is deactivated.
IVehicle speed memory is can-
celed.
IASCD brake switch or stop lamp switch is faulty.IASCD is deactivated.
IVehicle speed memory is not
canceled.
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AUTOMATIC SPEED CONTROL DEVICE (ASCD)
Fail-safe System
EL-229

Trouble DiagnosesNBEL0218SYMPTOM CHARTNBEL0218S01
PROCEDURE Diagnostic procedure
REFERENCE PAGE (EL- ) 231 232 233 234 235 235 237
SYMPTOM
FAIL-SAFE SYSTEM CHECK
POWER SUPPLY AND GROUND CIRCUIT CHECK
ASCD BRAKE/STOP LAMP SWITCH CHECK
ASCD STEERING SWITCH CHECK
VEHICLE SPEED SENSOR CHECK
ASCD PUMP CIRCUIT CHECK
ASCD ACTUATOR/PUMP CHECK
ASCD cannot be set. (ªCRUISEº indica-
tor lamp does not ON.)XXH3
ASCD cannot be set. (ªSETº indicator
lamp does not blink.)XXX
ASCD cannot be set. (ªSETº indicator
lamp blinks.H1)X XXXX
Vehicle speed does not decrease after
SET/COAST switch has been pressed.XX
Vehicle speed does not return to the set
speed after RESUME/ACCEL switch has
been pressed.H2XX
Vehicle speed does not increase after
RESUME/ACCEL switch has been
pressed.XX
System is not released after CANCEL
switch (steering) has been pressed.XX
Large difference between set speed and
actual vehicle speed.XXX
Deceleration is greatest immediately
after ASCD has been set.XXX
H1: It indicates that system is in fail-safe. After completing diagnostic procedures, perform ªFAIL-SAFE SYSTEM CHECKº (EL-231) to
verify repairs.
H2: If vehicle speed is greater than 40 km/h (25 MPH) after system has been released, pressing RESUME/ACCEL switch returns vehicle
speed to the set speed previously achieved. However, doing so when the ASCD main switch is turned to ªOFFº, vehicle speed will not
return to the set speed since the memory is canceled.
H3: Check only main switch built-in steering switch.
AUTOMATIC SPEED CONTROL DEVICE (ASCD)
Trouble Diagnoses
EL-230

SEL417V
FAIL-SAFE SYSTEM CHECK=NBEL0218S021. Turn ignition switch to ON position.
2. Turn ASCD main switch to ON and check if the SET indicator
blinks.
If the indicator lamp blinks, check the following.
IASCD steering switch. Refer to EL-234.
SEL767P
3. Drive the vehicle at more than 40 km/h (25 MPH) and push
SET/COAST switch.
If the indicator lamp blinks, check the following.
IVehicle speed sensor. Refer to EL-235.
IASCD pump circuit. Refer to EL-235.
IReplace control unit.
SAT797A
4. Depress brake pedal slowly (brake pedal should be depressed
more than 5 seconds).
If the indicator lamp blinks, check the following.
IASCD brake/stop lamp switch. Refer to EL-233.
5. END. (System is OK.)
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AUTOMATIC SPEED CONTROL DEVICE (ASCD)
Trouble Diagnoses (Cont'd)
EL-231

ASCD Wire Adjustment=NBEL0220
MEL383K
CAUTION:
IBe careful not to twist ASCD wire when removing it.
IDo not tense ASCD wire excessively during adjustment.
Adjust the tension of ASCD wire in the following manner.
1. Loosen lock nut and adjusting nut.
2. Make sure that accelerator wire is properly adjusted. Refer to
FE-3, ªACCELERATOR CONTROL SYSTEMº.
3. Tighten adjusting nut just until throttle drum starts to move.
4. Loosen adjusting nut again 1/2 to 1 turn.
5. Tighten lock nut.
AUTOMATIC SPEED CONTROL DEVICE (ASCD)
ASCD Wire Adjustment
EL-240

System DescriptionNBEL0102Power is supplied at all times
Ifrom 40A fusible link (letterf, located in the fuse and fusible link box)
Ito circuit breaker terminal 1
Ithrough circuit breaker terminal 2
Ito power window relay terminal 3,
Ito front power window main switch terminal 4, and
Ito front power window switch RH terminal 6.
With ignition switch in ON or START position, power is supplied
Ithrough 7.5A fuse [No. 11, located in the fuse block (J/B)]
Ito power window relay terminal 2, and
Ito smart entrance control unit terminal 33.
Ground is supplied to power window relay terminal 1
Ithrough body grounds M4, M66 and M147.
The power window relay is energized and power is supplied
Ithrough power window relay terminal 5
Ito front power window main switch terminal 11,
Ito front power window switch RH terminal 13,
Ito rear power window switch LH and RH terminals 5.
MANUAL OPERATIONNBEL0102S01Front Door LHNBEL0102S0101Ground is supplied
Ito front power window main switch terminal 5
Ithrough body grounds M77 and M111.
WINDOW UP
When the front LH switch in the front power window main switch is pressed in the up position, power is sup-
plied
Ito front power window regulator LH terminal 1
Ithrough front power window main switch terminal 2.
Ground is supplied
Ito front power window regulator LH terminal 3
Ithrough front power window main switch terminal 3.
Then, the motor raises the window until the switch is released.
WINDOW DOWN
When the LH switch in the front power window main switch is pressed in the down position, power is supplied
Ito front power window regulator LH terminal 3
Ithrough front power window main switch terminal 3.
Ground is supplied
Ito front power window regulator LH terminal 1
Ithrough front power window main switch terminal 2.
Then, the motor lowers the window until the switch is released.
Front Door RHNBEL0102S0102Ground is supplied
Ito front power window main switch terminal 5
Ithrough body grounds M77 and M111.
NOTE:
Numbers in parentheses are terminal numbers, when power window switch is pressed in the UP and DOWN
positions respectively.
FRONT POWER WINDOW MAIN SWITCH OPERATION
When front RH switch in the front power window main switch is pressed UP or DOWN, a signal is supplied
Ithrough front power window main switch terminal 8
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POWER WINDOW
System Description
EL-241

Ito front power window switch RH terminal 11.
The subsequent operation is the same as the front power window switch RH operation.
FRONT POWER WINDOW SWITCH RH OPERATION
Power is supplied
Ithrough front power window switch RH (5, 4)
Ito front power window regulator RH (1, 3).
Ground is supplied
Ito front power window regulator RH (3, 1)
Ithrough front power window switch RH (4, 5)
Ito front power window switch RH terminal 12
Ithrough front power window main switch terminal 1.
Then, the motor raises or lowers the window until the switch is released.
Rear Door LHNBEL0102S0104Ground is supplied
Ito front power window main switch terminal 5
Ithrough body grounds the M77 and M111.
NOTE:
Numbers in parentheses are terminal numbers, when the power window switch is pressed in the UP and
DOWN positions.
FRONT POWER WINDOW MAIN SWITCH OPERATION
Power is supplied
Ithrough front power window main switch terminal (13, 12)
Ito rear power window switch LH terminal (3, 4)
The subsequent operation is the same as the rear power window switch LH operation.
REAR POWER WINDOW SWITCH LH
Power is supplied
Ithrough rear power window switch LH (1, 2)
Ito rear power window regulator LH (1, 2)
Ground is supplied
Ito rear power window regulator LH (2, 1)
Ithrough rear power window switch LH (2, 1)
Ito rear power window switch LH terminal (4, 3)
Ithrough front power window main switch terminal (12, 13)
Then, the motor raises or lowers the window until the switch is released.
Rear Door RHNBEL0102S0105Rear door RH windows will rise and lower in the same manner as the rear door LH window.
AUTO OPERATIONNBEL0102S02The power window AUTO feature enables the driver or front passenger to open or close the driver's and front
passenger's window without holding the window switch in the up or down position.
The AUTO feature only operates on the driver's and front passenger's window upward and downward move-
ment.
POWER WINDOW LOCKNBEL0102S03The power window lock is designed to lock operation of all windows except for driver's door window.
When the lock switch is pressed to lock position, the ground of the front and rear power window switches, in
the power window main switch, is disconnected. This prevents the power window motors from operating.
RETAINED POWER OPERATIONNBEL0102S04When the ignition switch is turned to OFF position from ON or START position, power is supplied for 45 sec-
onds
Ito power window relay terminal 2
Ifrom smart entrance control unit terminal 5.
Ground is always supplied
POWER WINDOW
System Description (Cont'd)
EL-242