Cruise Control

This article explains how a typical automotive cruise control works, this information pertains to most vehicles.

A cruise control system can be set by using a small multi function switch to increase or decrease vehicle speed via the engine RPM. The cruise control switch location can vary from the steering wheel to a lever on the column.

Cruise Control (appearance will vary)
A cruise control system is used to control and maintain a consistent vehicle speed with the help of an electronic throttle or vacuum actuator which is connected to the engine throttle (older models).

Throttle Actuator
An electronic throttle actuator is controlled by the main computer which has recorded the desired setting from the driver.

Computer PCM
Using data feedback from the vehicle speed sensor VSS the computer can increase or decrease vehicle speed.

Vehicle Speed Sensor VSS
When the brake or clutch pedal is used the cruise control is released allowing the driver to slow the vehicle, using the resume button will cause the vehicle to return to the last recorded set speed (MPH).

Push Brake Pedal Down

Helpful Information

A laser or radar control system is known as an autonomous cruise control, or adaptive cruise control which sets the distance between cars. When the distance setting is compromised the vehicle speed is automatically decreased, then holds an alternative speed until the distance increases. A warning light is illuminated on the dash to alert the driver and is used to avoid collisions.


A cruise control system is also known by alternative names such as auto-cruise and speed control. A mechanical engineer by the name of Ralph Teetor in 1945, invented the Speedostat, which is a version of the modern cruise control system. The idea was conceptualized when Ralph observed a rotating drive shaft. Having knowledge of electronics he devised a counter and throttle actuator which was connected to the engine, throttle position was varied by the vacuum actuator. These first cruise control systems consisted of a control unit, drive shaft, control switch, brake cutoff switch, vacuum servo, wiring harness and vacuum lines.

Common Problems

  • Brake pedal cutoff switch can become maladjusted causing the cruise control not to engage.

Article first published