Infiniti QX4 (R50). Manual — part 351
Component Parts and Harness Connector
Location
NBEL0094
SEL362X
GI
MA
EM
LC
EC
FE
AT
TF
PD
AX
SU
BR
ST
RS
BT
HA
SC
IDX
AUTOMATIC SPEED CONTROL DEVICE (ASCD)
Component Parts and Harness Connector Location
EL-221
System Description
NBEL0216
Refer to Owner’s Manual for ASCD operating instructions.
POWER SUPPLY AND GROUND
NBEL0216S01
Power is supplied at all times:
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through 10A fuse [No. 14, located in the fuse block (J/B)]
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to the stop lamp switch terminal 1, and
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through 7.5A fuse (No. 52, located in fuse and fusible link box)
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to the horn relay terminals 1 and 3.
When ignition switch is in the ON or START position, power is supplied:
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through 7.5A fuse [No. 11, located in the fuse block (J/B)]
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to ASCD brake switch terminal 1 and
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to ASCD control unit terminal 5,
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through 10A fuse [No. 18, located in the fuse block (J/B)]
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to park/neutral position relay terminal 1,
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through 10A fuse [No. 8, located in the fuse block (J/B)]
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to combination meter terminal 66, and
When park/neutral position switch is in the P or N position, ground is supplied:
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to park/neutral position relay terminal 2
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through park/neutral position switch and body grounds B55 and B75.
When ASCD main switch is depressed (ON), ground is supplied:
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to ASCD control unit terminal 9
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from ASCD steering switch terminal 4
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to ASCD steering switch terminal 5
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through body grounds M4, M66 and M147
then ASCD control unit holds CRUISE condition and illuminates CRUISE indicator.
Ground is supplied:
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from ASCD control unit terminal 15
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to combination meter terminal 46.
OPERATION
NBEL0216S02
Set Operation
NBEL0216S0201
To activate the ASCD, all following conditions must exist.
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Ground supply to ASCD control unit terminal 9 (Main switch is in ON position.)
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Power supply to ASCD control unit terminal 8 (Brake pedal is released and A/T selector lever is in other
than P and N position.)
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Vehicle 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:
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from ASCD steering switch terminal 2
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to ASCD control unit terminal 11.
And then ASCD pump is activated to control throttle wire and ASCD control unit supply ground
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to combination meter terminals 51 to illuminate SET indicator.
A/T Overdrive Control during Cruise Control Driving
NBEL0216S0202
When the vehicle speed is approximately 3 km/h (2 MPH) below set speed, a signal is sent
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from ASCD control unit terminal 10
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to 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 Control
NBEL0216S0203
During ASCD cruise, ASCD control unit controls A/T shifting to avoid uncomfortable shifting.
This is used to control the signals below.
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Throttle position sensor from ECM
AUTOMATIC SPEED CONTROL DEVICE (ASCD)
System Description
EL-222
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A/T shift solenoid valve A
Coast Operation
NBEL0216S0204
When 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 Operation
NBEL0216S0205
When the RESUME/ACCEL switch is depressed, power is supplied
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from ASCD steering switch terminal 3
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to 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 Operation
NBEL0216S0206
When any of following condition exists, cruise operation will be canceled.
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CANCEL switch is depressed. (Power supply to ASCD control unit terminals 11 and 24)
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Brake pedal is depressed. (Power supply to ASCD control unit terminal 23 from stop lamp switch)
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Brake 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 Operation
NBEL0216S0207
When 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.
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Brake pedal is released.
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A/T selector lever is in other than P and N position.
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Vehicle speed is between 40 km/h (25 MPH) and 144 km/h (89 MPH).
ASCD PUMP OPERATION
NBEL0216S03
The ASCD pump consists of a vacuum motor, an air valve and a release valve. When the ASCD activates,
power is supplied
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from terminal 12 of ASCD control unit
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to 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 motor
Actuator inner pres-
sure
ASCD not operating
Open
Open
Stopped
Atmosphere
ASCD operating
Releasing throttle
cable
Open
Closed
Stopped
Vacuum
Holding throttle
position
Closed
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.
GI
MA
EM
LC
EC
FE
AT
TF
PD
AX
SU
BR
ST
RS
BT
HA
SC
IDX
AUTOMATIC SPEED CONTROL DEVICE (ASCD)
System Description (Cont’d)
EL-223
Schematic
NBEL0096
MEL837L
AUTOMATIC SPEED CONTROL DEVICE (ASCD)
Schematic
EL-224
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