IDX INFINITI QX4 2001 Factory Service Manual

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

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.
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

Wiring Diagram Ð ASCD ÐNBEL0097FIG. 1NBEL0097S01
MEL838L
GI
MA
EM
LC
EC
FE
AT
TF
PD
AX
SU
BR
ST
RS
BT
HA
SC
IDX
AUTOMATIC SPEED CONTROL DEVICE (ASCD)
Wiring Diagram Ð ASCD Ð
EL-225

FIG. 3NBEL0097S03
MEL840L
GI
MA
EM
LC
EC
FE
AT
TF
PD
AX
SU
BR
ST
RS
BT
HA
SC
IDX
AUTOMATIC SPEED CONTROL DEVICE (ASCD)
Wiring Diagram Ð ASCD Ð (Cont'd)
EL-227

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.
GI
MA
EM
LC
EC
FE
AT
TF
PD
AX
SU
BR
ST
RS
BT
HA
SC
IDX
AUTOMATIC SPEED CONTROL DEVICE (ASCD)
Fail-safe System
EL-229

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.)
GI
MA
EM
LC
EC
FE
AT
TF
PD
AX
SU
BR
ST
RS
BT
HA
SC
IDX
AUTOMATIC SPEED CONTROL DEVICE (ASCD)
Trouble Diagnoses (Cont'd)
EL-231

ASCD BRAKE/STOP LAMP SWITCH CHECK=NBEL0218S04
1 CHECK ASCD BRAKE SWITCH CIRCUIT
1. Disconnect ASCD control unit harness connector.
2. Turn ignition switch ON.
3. Check voltage between ASCD control unit harness connector terminal 8 and ground.
SEL258WD
OK or NG
OK©GO TO 2.
NG©Check the following.
IASCD brake switch
Refer to ªElectrical Component Inspectionº (EL-239).
IPark/neutral position switch
Refer to ªElectrical Component Inspectionº (EL-239).
IPark/neutral position relay
IHarness for open or short
2 CHECK STOP LAMP SWITCH CIRCUIT
1. Disconnect ASCD control unit harness connector.
2. Check voltage between ASCD control unit harness connector terminal 23 and ground.
SEL259WB
Refer to wiring diagram in EL-226.
OK or NG
OK©ASCD brake/stop lamp switch is OK.
NG©Check the following.
I10A fuse [No. 14, located in the fuse block (J/B)]
IHarness for open or short between ASCD control unit and stop lamp switch
IHarness for open or short between fuse and stop lamp switch
IStop lamp switch
Refer to ªElectrical Component Inspectionº (EL-239).
GI
MA
EM
LC
EC
FE
AT
TF
PD
AX
SU
BR
ST
RS
BT
HA
SC
IDX
AUTOMATIC SPEED CONTROL DEVICE (ASCD)
Trouble Diagnoses (Cont'd)
EL-233

VEHICLE SPEED SENSOR CHECK=NBEL0218S06
1 CHECK SPEEDOMETER OPERATION
Does speedometer operate normally?
Ye s©GO TO 2.
No©Check speedometer and vehicle speed sensor circuit. Refer to wiring diagram in EL-228.
2 CHECK VEHICLE SPEED INPUT
1. Apply wheel chocks and jack up drive wheel.
2. Disconnect ASCD control unit harness connector.
3. Check voltage between control unit terminal 22 and ground with turning drive wheel slowly by hand.
SEL263WB
Refer to wiring diagram in EL-227.
Ye s©Vehicle speed sensor is OK.
No©Check harness for open or short between ASCD control unit terminal 22 and combination
meter terminal 13.
ASCD PUMP CIRCUIT CHECKNBEL0218S07
1 CHECK ASCD PUMP
1. Disconnect ASCD pump connector.
2. Measure resistance between ASCD pump terminals 1 and 2, 3, 4.
SEL262WB
Refer to wiring diagram in EL-227.
OK or NG
OK©GO TO 2.
NG©Replace ASCD pump.
GI
MA
EM
LC
EC
FE
AT
TF
PD
AX
SU
BR
ST
RS
BT
HA
SC
IDX
AUTOMATIC SPEED CONTROL DEVICE (ASCD)
Trouble Diagnoses (Cont'd)
EL-235

ASCD ACTUATOR/PUMP CHECK=NBEL0218S08
1 CHECK VACUUM HOSE
Check vacuum hose (between ASCD actuator and ASCD pump) for breakage, cracks or fracture.
MEL402G
OK or NG
OK©GO TO 2.
NG©Repair or replace hose.
2 CHECK ASCD WIRE
Check wire for improper installation, rust formation or breaks.
OK or NG
OK©GO TO 3.
NG©Repair or replace wire. Refer to ªASCD Wire Adjustmentº (EL-240).
3 CHECK ASCD ACTUATOR
1. Disconnect vacuum hose from ASCD actuator.
2. Connect the hose of hand vacuum pump to ASCD actuator.
SEL264W
OK or NG
OK©GO TO 4.
NG©Replace ASCD actuator.
GI
MA
EM
LC
EC
FE
AT
TF
PD
AX
SU
BR
ST
RS
BT
HA
SC
IDX
AUTOMATIC SPEED CONTROL DEVICE (ASCD)
Trouble Diagnoses (Cont'd)
EL-237

SEL302X
Electrical Component Inspection=NBEL0219ASCD BRAKE SWITCH AND STOP LAMP SWITCHNBEL0219S02
ConditionContinuity
ASCD brake
switchStop lamp switch
When brake pedal is depressed No Yes
When brake pedal is released Yes No
Check each switch after adjusting brake pedal Ð refer to BR-14,
ªBRAKE PEDAL AND BRACKETº.
SEL303X
PARK/NEUTRAL POSITION SWITCHNBEL0219S03
A/T selector lever positionContinuity
Between terminals 1 and 2
ªPº Yes
ªNº Yes
Except ªPº and ªNº No
GI
MA
EM
LC
EC
FE
AT
TF
PD
AX
SU
BR
ST
RS
BT
HA
SC
IDX
AUTOMATIC SPEED CONTROL DEVICE (ASCD)
Electrical Component Inspection
EL-239