Cruise Control System Operation

The cruise control system is used to control vehicle speed to a user selected value and an accuracy of ± 2 km/h (1 mph) on a flat level road (± 2% grade).

The system consists of a cruise control module; located in the passenger compartment on the driver's side above the accelerator pedal, cruise control switches, stop lamp switch and PCM.

Unlike other cruise control systems, this system is fully electronic and does not require vacuum or a vacuum servo motor to control the movement of the throttle. To control throttle movement, a rod from the cruise control module pulls on the accelerator linkage at the accelerator pedal.

The cruise control system is an integration of the cruise control module and PCM. Cruise control signals go directly to the PCM, which in turn uses engine control sensors to evaluate and command cruise control movement, cruise control direction and enable/disable of the cruise control module clutch.

The stop lamp switch is used as an input to the PCM to enable/disable the cruise control clutch ground. With the brake pedal released, the stop lamp switch also allows ignition voltage at the cruise control module. This voltage turns a driver On which allows current to flow to the cruise control clutch. When the brake pedal is depressed, the PCM will open the ground circuit and the cruise control module will open the ignition voltage circuit to the cruise control clutch. This ensures that the clutch is turned Off when the brake pedal is depressed.

The cruise control module uses the cruise control clutch to engage the drive motor to the attachment rod mechanism. The speed and direction at which the rod moves is determined by the PCM and conveyed to the cruise control module through the cruise control move and direction circuits. The PCM will supply ignition voltage on the cruise control direction circuit when the accelerator pedal needs to move toward wide-open-throttle to maintain cruise set speed. If the PCM commands the pedal toward idle, the voltage will go low. When no movement is needed, the PCM defaults to the toward idle state.

The PCM pulse width modulates ignition voltage on the cruise move circuit which provides the amount and speed movement of the accelerator pedal. Very short On-time pulses indicate a steady accelerator position. The longer the On-time pulses (up to a 90% duty cycle), the faster the accelerator pedal will move.