Automatic Speed Control Device (ASCD)
Automatic Speed Control Device (ASCD)System Description
Refer to Owner's Manual for ASCD operating instructions.
POWER SUPPLY AND GROUND
Power is supplied at all times:
- through 10 A fuse [No. 14, located in the fuse block (J/B)]
- to the stop lamp switch terminal 1, and
- through 7.5 A fuse (No. 52, located in fuse and fusible link box)
- to the horn relay terminals 1 and 3.
When ignition switch is in the ON or START position, power is supplied:
- through 7.5 A fuse [No. 11, located in the fuse block (J/B)]
- to ASCD brake switch terminal 1 and
- to ASCD control unit terminal 5,
- through 10 A fuse [No. 18, located in the fuse block (J/B)]
- to park/neutral position relay terminal 1,
- through 10 A fuse [No. 8, located in the fuse block (J/B)]
- to combination meter terminal 66, and
When park/neutral position switch is in the P or N position, ground is supplied:
- to park/neutral position relay terminal 2
- through park/neutral position switch and body grounds B55 and B75.
When ASCD main switch is depressed (ON), ground is supplied:
- to ASCD control unit terminal 9
- from ASCD steering switch terminal 4
- to ASCD steering switch terminal 5
- through body grounds M4, M66 and M147 then ASCD control unit holds CRUISE condition and illuminates CRUISE indicator.
Ground is supplied:
- from ASCD control unit terminal 15
- to combination meter terminal 46.
OPERATION
Set Operation
To activate the ASCD, all following conditions must exist.
- Ground is supplied to ASCD control unit terminal 9 (Main switch is in ON position.)
- Power is supplied to ASCD control unit terminal 8 (Brake pedal is released and A/T selector lever is in other than P and N position.)
- 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:
- from ASCD steering switch terminal 2
- to ASCD control unit terminal 11.
And then ASCD pump is activated to control throttle wire and ASCD control unit supply ground
- to combination meter terminals 51 to illuminate SET indicator.
A/T Overdrive Control during Cruise Control Driving
When the vehicle speed is approximately 3 km/h (2 MPH) below set speed, a signal is sent
- from ASCD control unit terminal 10
- 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
During ASCD cruise, ASCD control unit controls A/T shifting to avoid uncomfortable shifting. This is used to control the signals below.
- Throttle position sensor from ECM
-
- A/T shift solenoid valve A
Coast Operation
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
When the RESUME/ACCEL switch is depressed, power is supplied
- from ASCD steering switch terminal 3
- 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
When any of following condition exists, cruise operation will be canceled.
- CANCEL switch is depressed. (Power supply to ASCD control unit terminals 11 and 24)
- Brake pedal is depressed. (Power supply to ASCD control unit terminal 23 from stop lamp switch)
- Brake pedal is depressed or A/T selector lever is shifted to P or N position. (Power supply to ASCD control 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
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.
- Brake pedal is released.
- A/T selector lever is in other than P and N position.
- Vehicle speed is between 40 km/h (25 MPH) and 144 km/h (89 MPH).
ASCD PUMP OPERATION
The ASCD pump consists of a vacuum motor, an air valve and a release valve. When the ASCD activates, power is supplied
- from terminal 12 of ASCD control unit
- 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 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.