Cruise Control: Description and Operation

How the L4 Circuit Works

The cruise control system uses mechanical and electrical devices to maintain the car's speed at a setting selected by the driver.

Power Supply

With the ignition switch in the ON (II) or START (III) position, battery voltage is applied through fuse 18 to the cruise control unit and through fuse 21 to the gauge control module.

Fuse 7 is hot at all times and supplies battery voltage to the relay control module.

Fuse 13 is hot at all times and supplies battery voltage to the cruise control unit when the brake pedal position switch is closed (brake pedal pressed).

System Description

The cruise control unit receives information signals about operating conditions from the main switch, set switch, cancel switch, and the resume switch in the steering wheel.

The cruise control unit also receives information from the brake pedal position switch, the ECM/PCM, the clutch pedal position switch (M/T), and the gauge control module.

The cruise control unit then sends signals to the cruise control actuator, which regulates the throttle position to maintain the selected speed. The control unit compares the actual speed of the car to the selected speed, and then opens or closes the throttle as necessary to match the selected speed.

The brake pedal position switch releases the system's control of the throttle at the instant you press on the brake pedal. The switch sends a signal to the control unit by applying battery voltage to the cruise control unit from the normally open brake input. The brake pedal position switch also allows communication between the cruise control actuator and the cruise control unit when the pedal is pressed. The control unit responds by allowing the throttle to fully close.

The clutch pedal position switch (M/T) sends a "disengage" ground signal to the cruise control unit that allows the throttle to close (cruise deactivated) when the clutch pedal is pressed.

The transmission range switch (A/T) will also sends a "disengage" signal to the ECM/PCM and then sends a disengage signal to the cruise control unit.

The cruise control system will set and automatically maintain any speed above 25 mph (40 km/h). To set the cruise, make sure the main steering wheel switch is on and the CRUISE MAIN light is illuminated. After reaching the desired speed, press the DECEL/SET switch. This sends a "set" signal to the cruise control unit, which, in turn, controls the cruise control actuator to maintain the set speed. When you push the DECEL/SET switch to set the cruise, the CRUISE CONTROL indicator on the gauge control module lights up. You can cancel the cruise control system by pushing the cancel switch or by turning the main switch off.

If the system is disengaged temporarily by the brake pedal position switch, transmission range switch or clutch pedal position switch (M/T), and the car's speed is still above 25 mph, pressing the RES/ACCEL switch will automatically return to the previously set speed.

For gradual acceleration without pressing the accelerator pedal, push the RES/ACCEL switch and hold it there. To increase the speed in very small amounts, tap the RES/ACCEL switch one time for each one mph of increase.

To slow the car down, push the DECEL/SET switch in and hold it there. To decrease the speed in very small amounts, tap the RES/ACCEL switch one time for each one mph of decrease.