Automatic Speed Control Device (ASCD)
System DescriptionPOWER SUPPLY AND GROUND CIRCUIT
Power is supplied at all times
- through 20 A fuse (No.22, located in the fuse block)
- to stop lamp switch terminal 1.
When ignition switch is in the ON or START position, power is supplied
- through 10 A fuse (No.29, located in the fuse block)
- to ASCD brake switch terminal 1
- to combination meter terminal 2 and
- to ASCD control unit terminal 5.
Ground is supplied
- to ASCD control unit terminal 17
- through body grounds M68, M105 and M130.
OPERATION
Set Operation
To activate the ASCD, all of following conditions must exist.
- ASCD control unit receives ASCD MAIN switch ON signal
- Power supply to ASCD control unit terminal 8 (Brake pedal is released and A/T selector lever is in other than P and N positions.)
- 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 5
- to ASCD control unit terminal 11.
Then ASCD actuator is activated to control throttle wire and ASCD control unit terminal 18 supplies ground
- to combination meter terminal 18 to illuminate SET indicator.
A/T Overdrive Control During Cruise Control Driving
When the vehicle speed is approximately 8 km/h (5 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 cancels overdrive.
After vehicle speed is approximately 3 km/h (2 MPH) above 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 following signals.
- Throttle position sensor from ECM A/T shift solenoid valve
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. Then ASCD will keep the new set speed.
Accel Operation
When the RESUME/ACCEL switch is depressed, ground is supplied
- from ASCD steering switch terminal 5
- to ASCD control unit terminal 11.
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. Then ASCD will keep the new set speed.
Cancel Operation
When any of the following condition exists, cruise operation will be canceled.
- CANCEL switch is depressed (ground is supplied to ASCD control unit terminal 11).
- Brake pedal is depressed (power is supplied to ASCD control unit terminal 23 from stop lamp switch and power supply to ASCD control unit terminal 8 is interrupted.)
- 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 depressed while 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), 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 or N position
- Vehicle speed is between 40 km/h (25 MPH) and 144 km/h (89 MPH).
ASCD ACTUATOR OPERATION
The ASCD actuator consists of a vacuum valve, an air valve and a release valve. When the ASCD activates, power is supplied
- from terminal 12 of ASCD control unit
- to ASCD actuator terminal 1.
Ground is supplied to vacuum valve, air valve and release valve from ASCD control unit depending on the operating condition as shown in the table.
When the vacuum valve is opened, the vacuum is applied to the diaphragm of ASCD actuator through ASCD vacuum tank to control throttle cable.