The auto-cruise control-ECU consists of the input interface circuit, microprocessor, constant voltage power supply circuit, microprocessor monitor circuit and output interface circuit. Vehicle signals from the engine-A/T-ECU, TPS and each switch are input into the auto-cruise control-ECU. It processes them according to the program in the microprocessor memory and outputs control signals to the actuator. It also outputs system self-diagnosis results and conditions of input signals to the diagnosis connector.
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 actuator is controlled so that fixed-speed driving at that speed is possible. However, the fixed-speed driving can not be set if the vehicle is being driven at a predetermined high speed limit or more.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 40 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 is 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:
- The vehicle speed is less than 130 km/h, and during fixed speed travel, the actual vehicle speed decreases from the preset speed by 7 km/h.
CANCEL FUNCTION
When any of the following conditions occur, the power supply to the motor-driven negative pressure pump is shut off and the auto-cruise control is cancelled.- "CANCEL" switch ON
- Stop lamp switch ON (brake is applied)
- Inhibitor switch is "N" position
- Vehicle speed at the low-speed limit (about 40 km/h) or lower
- Vehicle speed going lower than memorized speed by 15 km/h or more
- Vehicle speed once increasing to memorized speed less 10 km/h and then decreasing more than 15 km/h during
- Vehicle speed changing sharply
- Stop lamp switch input malfunction or open circuit
FAIL-SAFE FUNCTION
When any of the following conditions are met, the power supply to the auto-cruise vacuum pump is shut off and the auto-cruise control stops entirely or cancels while driving.| Condition |
Auto-cruise stopped |
Auto-cruise cancelled |
|---|---|---|
| "SET" or "RESUME" switch held ON for 60 seconds or more |
Yes |
Yes |
| Fault in cancel state holding circuit |
Yes |
Yes |
| Auto-cruise vacuum pump drive signal and valve drive signals not matching |
Yes |
Yes |
| Vehicle speed signal failing to be input for 0.1 seconds or longer |
Yes |
Yes |
| "MAIN" switch held ON for five seconds or more |
Yes |
Yes |
| Auto-cruise control-ECU power voltage continues at a state of 4V or more, 9V or less for four seconds or more during fixed speed travel. |
Yes |
Yes |
| Failed TPS |
Yes |
No |
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 |
|---|---|
| 11 |
Abnormality in auto-cruise vacuum pump drive system |
| 12 |
Abnormality in vehicle speed signal system |
| 14 |
Defective stop lamp switch/brake switch |
| 15 |
Defective auto-cruise control switch |
| 16 |
Defective auto-cruise control-ECU |
| 17 |
Defective throttle position sensor and idle position signal system |
HOW TO ERASE DISPLAY DIAGNOSIS CODE
Use the MUT-II/III to erase the diagnosis code.SERVICE DATA OUTPUT
The service data output are 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 |
|
| 08 |
Accelerator switch (Idle switch) |
ON/OFF |
|
| 10 |
Vehicle speed signal |
km/h |
|
| 13 |
Throttle position sensor (TPS) |
mV |
|
| 14 |
Inhibitor switch |
ON/OFF |
|
| 15 |
Over drive detective |
ON/OFF |
|
NOTE: If two or more actions are taken at the same time, codes are set in ascending order of code number.