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Your Vehicle’s Cruise Control Isn’t Working? Here Are the Most Common Causes

If you frequently drive long distances, the innovative cruise control system is invaluable, but sometimes it might stop functioning. This article explores the potential causes and what you can do to fix this annoying issue.
Alfa Romeo steering wheel 6 photos
Photo: Łukasz Nieścioruk on Unsplash
FusesMustang TaillightsCars Cruising on the HighwayFuse BoxHella Brake Switch
Designed to reduce stress and fatigue when driving for long distances, the version of the system we use today was invented in 1948 by blind mechanical engineer Ralph Teetor who was frustrated that his driver kept speeding up and slowing down on highways.

When engaged, cruise control maintains a selected speed without requiring direct driver input. Speed can be increased or decreased using the cruise control buttons, which are usually located on the steering wheel. Drivers can disable it at any time by simply tapping on the accelerator or brake pedal.

The brain of the system is the cruise control module (CCM) which records the speed at which the vehicle is driven and takes control of the throttle body to maintain it.

Cars Cruising on the Highway
Photo: tookapic from Pixabay
Over the years, the way the throttle body is controlled has changed dramatically. The very first systems used a vacuum motor and cable that were eventually replaced by electric motors.

Modern cruise control systems use drive-by-wire or electronic throttle control systems (ETCS), with the feature integrated into the engine control module (ECM), which controls the throttle body.

Regardless of the design, this system is not failproof, and several factors can lead it to stop functioning.

Check engine light

Vehicles equipped with ETCS will automatically disable cruise control if there’s a problem with the engine or transmission, so if a check engine light lights up after starting the engine, get the vehicle to a mechanic as soon as possible.

Taillight bulbs and brake switch

Mustang Taillights
Photo: Joey Banks on Unsplash
In many vehicles, a problem with the brake lights will permanently disengage the system. If one of the bulbs inside the taillights is blown, have it replaced and check if the cruise control can now be engaged.

If none of the brake lights are working, then the culprit might be the brake light switch. This component is usually connected to the brake pedal and engages the lights when you press it.

It’s not expensive to replace, but it might prove difficult to do it yourself, so we recommend that you take the vehicle to a professional mechanic.

Fuses and relays

Fuse Box
Photo: howardmizuki from Pixabay
In some vehicles, fuses and relays are used to protect the system, so a blown one can cause the cruise control to stop functioning.

Check the fuse box, which is located either in the engine bay or behind the glovebox. For the exact location of the cruise control fuse and relay, check your vehicle’s owner manual.

Faulty speed sensor

Every modern vehicle usually has multiple speed sensors, and the CCM uses data from at least one of them to maintain the desired speed. If it happens to fail, which is not at all uncommon, then the whole system will stop functioning.

Vacuum Leak

Like I mentioned before, older vehicles use vacuum actuators to control the throttle body when cruise control is engaged. If there’s a leak in one of the hoses, then the system will be disabled.

Vacuum leaks can also cause the engine to idle at higher RPMs, so keep an eye on the tachometer. If you notice any irregularities, you need to take the vehicle to a mechanic who can identify and fix this leak.

If the problem persists even after all the above components were checked and found to function properly, then the cause lies in the vehicle’s electrical system. The cruise control button itself or one of the numerous wires can cause this issue, but to properly identify the source, a qualified automotive electrician needs to perform a comprehensive set of checks.
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About the author: Vlad Radu
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Vlad's first car was custom coach built: an exotic he made out of wood, cardboard and a borrowed steering wheel at the age of five. Combining his previous experience in writing and car dealership years, his articles focus in depth on special cars of past and present times.
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