SYSTEM OUTLINE
The engine-A/T-ECU calculates the cruise control operation status when the control section of the cruise control inside the engine-A/T-ECU receives the input signals of the auto-cruise control switch, vehicle speed, and cancel system (stop lamp switch and inhibitor switch). To the engine control section it sends the target accelerator angle value for cruise control, to the A/T control section it issues a command to cancel OD, and to the gauge it issues an ON/OFF command for the auto-cruise control indicator lamp. In the engine control section, the target throttle angle value is calculated from the target acceleration value for cruise control and the actual accelerator angle value, and the vehicle speed is controlled by applying the throttle valve control servo.BLOCK DIAGRAM
)
"SET/COAST" SWITCH FUNCTION
SET
The vehicle speed at the moment the "SET" switch was switched from ON to OFF while driving within the limit vehicle speed range is memorized as the "set vehicle speed" and thereafter the throttle actuator control motor is controlled so that fixed-speed driving at that speed is possible. However, if the vehicle speed is set at 200 km/h or higher, the speed of 200 km/h is saved as the vehicle speed, but if the vehicle speed is set above 205 km/h , the vehicle will not reach the specified speed.COAST
While the "COAST" switch is held ON during auto-cruise driving, the vehicle keeps decelerating. If the "COAST" switch is turned OFF before the vehicle speed decreases to 40 km/h, the vehicle runs at the fixed speed at the moment the switch is turned OFF. If the "COAST" switch is turned OFF after the vehicle speed decreases to less than 35 km/h, the auto-cruise control is cancelled. However if the "COAST" switch has been ON for 0.5 second or less, a tap-down operation is performed (decelerating from the current speed by 1.6 km/h). At over 0.5 second, continuous deceleration is performed."ACC/RES" SWITCH FUNCTION
RESUME
When fixed speed driving is cancelled by the conditions given in "CANCEL FUNCTION," switching the "RESUME" switch from OFF to ON while driving at a speed higher than the set speed causes the vehicle to be driven at a fixed speed which is the speed memorized just before cancelling.ACCELERATING
While the "ACCELERATING" switch is ON during fixed speed driving, the vehicle accelerates to the target speed. The vehicle speed at the moment the switch is turned OFF is then memorized and the vehicle remains at this for fixed speed. When the "ACCELERATING" switch is ON, the vehicle may accelerate to speeds above the high-speed limit but after the "ACCELERATING" switch is turned OFF, the vehicle will remain at this high-speed limit. However, if the "ACCELERATING" switch has been ON for 0.5 second or less, a tap-down operation is performed (accelerating from the current speed by 1.6 km/h). At over 0.5 second, acceleration is performed continuously.OVERDRIVE-CANCEL FUNCTION
When during fixed speed driving, the actual vehicle speed decreases to (or below) the memorized speed, the overdrive is cancelled temporarily, the memorized speed is restored when driving conditions allow. Overdrive is cancelled in the following case:- When the set speed can not be maintained with the current gear ratio due to insufficient drive power under constant speed control mode.
- When a proper acceleration can not be obtained with the current gear ratio due to insufficient drive power during the driver's acceleration switch operation (under acceleration mode).
- When a proper acceleration can not be obtained with the current gear ratio due to insufficient drive power after the driver's resume switch operation until being the set speed.
CANCEL FUNCTION
When any of the following conditions occur, the auto-cruise control is cancelled.- "MAIN" switch OFF
- "CANCEL" switch ON
- Stop lamp switch ON (brake is applied)
- Brake switch ON (brake is applied)
- Inhibitor switch in "P" "N" or "R" position
- The vehicle speed is about 35 km/h or lower
- Vehicle speed is lower than memorized speed by 15 km/h or more
- Vehicle speed once increasing to memorized speed less than 10 km/h and then decreasing more than 15 km/h with "RESUME" switch ON
- Vehicle speed changing sharply
- Stop lamp switch input (malfunction or open circuit)
- Defective auto-cruise control switch input voltage
- When the cancel latch signal is ON (The cancel latch signal is ON when the signal of the engine control section and the signal of the cruise control section in engine-A/T-ECU do not accord each other).
FAIL-SAFE FUNCTION
When any of the following conditions are met and do not activate auto-cruise control, and if the requirements are met during auto-cruise control, auto-cruise control is cancelled instantly. At this time, after the regular state is restored, auto-cruise control is possible again.- "SET" or "RESUME" switch held ON for 60 seconds or more.
- Fault in cancel state holding circuit
- The vehicle speed signal fails to be input for 0.1 second or longer during the vehicle speed is 40 km/h or more.
- During fixed-speed driving, if the vehicle exceeds the set speed by 10 km/h, the fixed-speed control is cancelled momentarily, then resumed after the vehicle speed exceeds the set speed by 7 km/h or less.
- Defective engine-A/T-ECU
- Defective throttle position sensor
- Defective accelerator pedal position sensor
SELF-DIAGNOSIS AND SERVICE DATA OUTPUT FUNCTIONS
SELF-DIAGNOSIS
When the auto-cruise control system operation cancels without driver input determine the cause simply by reading the diagnosis code.DIAGNOSIS CODE CHART
| Code No. |
Major contents of diagnosis |
|---|---|
| 15 |
Defective auto-cruise control switch |
| 21 |
Defective cancel latch |
| 22 |
Defective stop lamp switch/brake switch |
| 23 |
Defective in engine-A/T-ECU |
HOW TO ERASE DISPLAY DIAGNOSIS CODE
Use the MUT-II/III to erase the diagnosis code.SERVICE DATA OUTPUT
The service data output is shown in the following.| Items No. |
Service data item |
Unit |
|
|---|---|---|---|
| 01 |
Auto-cruise control switch |
"MAIN" |
ON/OFF |
| 02 |
"SET/COAST" |
ON/OFF |
|
| 03 |
"RESUME/ACCELERATING" |
ON/OFF |
|
| 04 |
"CANCEL" |
ON/OFF |
|
| 05 |
Stop lamp switch |
ON/OFF |
|
| 06 |
Brake switch |
ON/OFF |
|
| 07 |
Inhibitor switch |
ON/OFF |
|
| 08 |
Closed throttle position switch |
ON/OFF |
|
| 09 |
Auto-cruise control operation |
ON/OFF |
|
| 10 |
Vehicle speed signal |
km/h |
|
| 11 |
Throttle position sensor |
mV |
|
| 12 |
Accelerator pedal position sensor |
mV |
|
| 13 |
Cancel code |
Displays a cancel code number. |
|
NOTE: If two or more actions are taken at the same time, codes are set in ascending order of code number.