Cruise Control - STi

Cruise Control

OPERATION
- The cruise control system automatically controls the vehicle speed. It allows the vehicle to run at a constant speed without need for the driver to keep the accelerator pedal depressed.
- The cruise control system is controlled by the engine control module (ECM).
- When the driver has activated the system and made a desired speed setting, the engine control module (ECM) compares the actual vehicle speed detected by the speed sensor with the preset speed in the engine control module (ECM) memory, and then generates a signal according to the difference between the two speeds.

This signal is transmitted to the electronic control throttle.
The electronic control throttle operates the throttle valve as necessary to keep the preset vehicle speed.




CONTROL AND OPERATION

COMMAND SWITCH (CRUISE CONTROL LEVER)




- When the vehicle is driven with the cruise control activated, the command switch controls its operation. It inputs MAIN signal, SET/COAST signal, ACCEL/RESUME signal or CANCEL signal to the engine control module (ECM).
- When the cruise control MAIN switch is turned ON, the cruise set indicator light in the combination meter illuminates. Also, when the cruise control is set, the cruise indicator light in the combination meter illuminates.
- The command switch is located on the right side of the steering wheel, so the driver can operate it without releasing hands from the steering wheel.
- The command switch is a self-returning lever type.

1. MAIN SWITCH
When the switch is pushed once the cruise control system turns ON and becomes ready to set the cruise control. When the switch is pushed again the cruise control turns OFF.

2. RESUME/ACCEL AND SET/COAST SWITCH
Each switch contact is held closed as long as the lever is kept pressed in the relevant direction and resulting current is applied as a signal to the engine control module (ECM).

3. CANCEL SWITCH
All the switch contacts are closed as long as the lever is pulled toward the CANCEL position (toward the driver). This causes the RESUME/ACCEL and SET/COAST ON signals to be sent to the engine control module (ECM) simultaneously.

CANCEL SIGNALS
The cancel signal deactivates the cruise control function. Operating any of the following switches results in generation of the cancel signal. On receiving the signal, the engine control module (ECM) cancels the cruise control function.
- Stop light switch
- Brake switch
- Clutch switch
- Neutral switch
- MAIN switch (OFF operation)
- Command switch (CANCEL position)
- Ignition switch (OFF operation)

VEHICLE SPEED SENSOR
The vehicle speed sensor is installed on the transmission, and sends signal to the engine control module (ECM) which uses it in controlling the cruise control function.

ENGINE CONTROL MODULE (ECM)




- Based on signals from the related switches and sensors, the engine control module (ECM) controls all the following control functions:

Constant speed control; speed setting control; deceleration control; acceleration control; resume control; manual cancel control; low speed limit control; electronic control throttle control

- The engine control module (ECM) (A) is located in the legroom of the front passenger's seat.

FAIL-SAFE FUNCTION
The cruise control system has a fail-safe function that cancels the cruise control operation when any of the following conditions occurs.

1. CONFLICT BETWEEN CRUISE CONTROL SWITCHES AND CANCELLATION SIGNAL GENERATING SWITCHES
- The cruise control system is deactivated if any of the cruise control switches (SET/COAST, RESUME/ACCEL, and CANCEL switches) is turned ON while any of the cancellation signal generating switches (brake, stop light, clutch, and neutral switches) is being operated. The system is re-activated when the cruise control switch is turned OFF and then turn ON again after the cancellation signal generating switch has been returned to its released position.
- When the MAIN switch is turned ON while any of the command switches is in the ON position, the cruise control system is deactivated. The system deactivating function is retained until the MAIN switch is turned OFF.

2. ABNORMALITIES IN ELECTRIC CIRCUITS
The cruise control system is deactivated and the set speed is also canceled if any of the following abnormalities occurs in the system's electric circuits.
- The system deactivation function is retained until the ignition switch is turned OFF.
- Abnormality of the command switch is detected.
- Abnormality of the stop light switch and brake switch is detected.
- Abnormality of the neutral switch is detected.
- Abnormality of the ignition switch is detected.
- Change in vehicle speed signal is detected.
- Abnormality in any of the engine related sensors is detected.
- Abnormality of the brake switch input circuit in the engine control module (ECM) is detected.
- The MAIN switch and command switch were already ON when the ignition switch is turned ON.

3. CRUISE CONTROL CANCEL FUNCTION
- When any of the following conditions is met, the cruise control is cancelled.
- To set the cruise control again, the vehicle speed must be returned to within the speed setting range and necessary conditions must be met.
- Abnormal engine speed acceleration is detected.
- The vehicle speed has dropped below the lower control limit during cruise control driving.
- The vehicle has been running at speed higher than the set speed for an abnormally long time during cruise controlled driving.
- The set speed became impossible to be maintained for some reason (steep upgrade, hand brake operation, abnormal engine power drop, etc.).