Car care · Elgin Auto Sales & Service Center · Elgin, IL
Adaptive Cruise Control: How It Works and How to Use It
Adaptive cruise control (ACC) keeps a set speed like regular cruise control, but it also slows down to keep a following distance from the vehicle ahead. Systems differ by brand, so this guide uses one owner's manual as its example, the 2026 Ram 1500, to show how ACC is turned on, set, adjusted and cancelled, and where its limits are.
20 mphminimum set speed in the manual example
4 distance settingsone bar (short) to four bars (longest)
Radar + cameradetect the vehicle ahead
Not a safety systema convenience feature
The short answer
In the manual example, ACC uses a radar sensor and a forward facing camera to detect a vehicle directly ahead. If it detects one, it applies limited braking or acceleration, never above your set speed, to keep a preset following distance. The manual says ACC is a convenience system, not a safety system, and is not designed to prevent collisions; the driver stays responsible for braking.
What adaptive cruise control does
In the manual example, ACC increases the driving convenience of cruise control on highways and major roadways, and lets you keep cruise control engaged in light to moderate traffic without constantly resetting your speed. If the ACC sensor detects a vehicle ahead, it applies limited braking or acceleration, not to exceed the original set speed, to keep a preset following distance while matching the speed of the vehicle ahead.
In vehicles not equipped with Active Driving Assist, Fixed Speed Cruise Control (if equipped) can be used when ACC is not enabled and functions as normal cruise control. The manual warns that in Fixed Speed Cruise Control mode the system will not react to vehicles ahead and no proximity warning sounds, so always be aware which mode is selected. To switch between the two, turn ACC off first with its on/off button, then turn on Fixed Speed Cruise Control.
From the 2026 Ram 1500 Owner's Manual (Cruise Control Systems and Adaptive Cruise Control (ACC), pages 262 and 263; To Set A Desired ACC Speed, page 265), read November 4, 2026.
How to turn it on and set a speed
The manual example puts the ACC buttons on the right side of the steering wheel:
- Push and release the ACC on/off button. The instrument cluster display shows "ACC Ready."
- When you reach the speed you want, push SET (+) or SET (-) and release. The display shows the set speed.
- Tap SET (+) or SET (-) to change the set speed by 1 mph per tap, or hold the button to change it in 5 mph steps.
- Push RES to return to the last set speed, then take your foot off the accelerator pedal.
The minimum set speed is 20 mph; if ACC is set below that, the set speed defaults to 20 mph. ACC cannot be engaged in 4WD Low, with the brakes or parking brake applied, in PARK, REVERSE or NEUTRAL, when the brakes are overheated, or when ESC Full Off mode is active, among other conditions the manual lists. Keeping your foot on the accelerator can take you past the set speed; the display then shows "ACC Driver Override," and while you keep accelerating past the set speed, ACC does not control the distance to the vehicle ahead.
From the 2026 Ram 1500 Owner's Manual (ACC Operation, Activating ACC, To Set A Desired ACC Speed, To Resume and To Vary The Speed Setting, pages 264 to 266), read November 4, 2026.
Setting the following distance
The manual example offers four distance settings, shown as bars in the instrument cluster display:
Four bars
Longest following distance.
Three bars
Long following distance.
Two bars
Medium following distance.
One bar
Short following distance.
Push the Distance Increase or Distance Decrease button to change the setting one bar at a time. ACC uses the setting and your speed to calculate the distance to the vehicle ahead. Its maximum braking is limited, and if ACC predicts that is not enough, "BRAKE!" flashes in the display and a chime sounds so you can brake yourself. From the 2026 Ram 1500 Owner's Manual (Setting The Following Distance In ACC, pages 266 and 267), read November 4, 2026.
Stop and go in traffic
In the manual example, ACC can slow the vehicle to a full stop while following the vehicle in front. If that vehicle starts moving within two seconds of your vehicle stopping, your vehicle resumes on its own. If it does not, you push RES or press the accelerator pedal to re-engage ACC at the existing set speed.
The manual warns that when ACC is resumed, the driver must make sure there are no pedestrians, vehicles or objects in the vehicle's path. It also lists an Overtake Aid: while following a vehicle with ACC engaged, using the left turn signal gives extra acceleration, up to the set speed, to help you pass on the left.
From the 2026 Ram 1500 Owner's Manual (When ACC Is Active, page 266; Overtake Aid and ACC Operation At Stop, page 267), read November 4, 2026.
Cancelling and turning it off
In the manual example, ACC is cancelled when the brake pedal is applied, the CANC button is pushed, ABS, ESC/TCS or Trailer Sway Control activates, the parking brake is applied, the gear selector leaves DRIVE, or the brakes overheat, among other listed conditions. It turns off and clears the set speed when you push the ACC on/off button, turn the ignition OFF or engage 4WD Low.
The manual also warns that leaving ACC on when you are not using it is dangerous, because you could set it by accident, and says to always leave the system off when you are not using it.
From the 2026 Ram 1500 Owner's Manual (To Activate/Deactivate, To Cancel and To Turn Off, pages 264 and 265), read November 4, 2026.
When not to use adaptive cruise control
The manual example says not to use ACC:
Bad weather
In fog, heavy rain, heavy snow or sleet.
Heavy or complex traffic
In heavy traffic and complex driving situations, such as highway construction zones.
Ramps and difficult roads
When entering a turn lane or highway off-ramp, or on roads that are winding, icy, snow-covered, slippery, or have steep uphill or downhill slopes.
Towing on steep grades
When towing a trailer up or down steep slopes, or whenever circumstances do not allow safe driving at a constant speed.
From the 2026 Ram 1500 Owner's Manual (Adaptive Cruise Control warning, page 263), read November 4, 2026.
What adaptive cruise control may not detect
The manual example says ACC does not react to pedestrians, oncoming vehicles or stationary objects, such as a stopped vehicle in a traffic jam or a disabled vehicle. If the vehicle you are following leaves your lane and a stopped vehicle is ahead, ACC will not react to it.
It also lists situations where ACC may brake late or unexpectedly: a vehicle offset in your lane or merging from the side, curves and hills, a vehicle that is not yet completely in your lane, and narrow vehicles near the edge of the lane. The driver needs to stay alert and may need to intervene. For towing, the manual recommends ACC only with an Integrated Trailer Brake Controller, because aftermarket controllers will not activate the trailer brakes when ACC is braking.
From the 2026 Ram 1500 Owner's Manual (Adaptive Cruise Control warning, page 263; Precautions While Driving With ACC, pages 269 and 270), read November 4, 2026.
ACC warning messages
Wipe Front Radar Sensor
Conditions such as snow, heavy rain, mud, dirt or ice limit the radar and the system deactivates. Fixed Speed Cruise Control is still available. If weather is not a factor, examine the sensor; if the message occurs frequently with no obstruction, the manual says to have the radar sensor realigned at an authorized dealer.
Clean Front Windshield
Poor visibility, an obstructed windshield, driving into the sun or fog on the inside of the glass can limit the camera, and the system has degraded performance until the condition clears.
Service Required
There may be an internal fault or a temporary malfunction. The vehicle is still drivable under normal conditions; try ACC again after an ignition cycle, and if the problem persists, the manual says to see an authorized dealer.
From the 2026 Ram 1500 Owner's Manual (Display Warnings And Maintenance, page 268), read November 4, 2026.
Service at Elgin Auto Sales & Service Center
Our service department works on all makes and models. If an ACC warning keeps coming back, schedule a visit and tell us the exact message you see. Your owner's manual may direct some repairs, such as radar sensor realignment, to an authorized dealer.
Our service department at 1200 E. Chicago St. in Elgin is open Monday to Friday 8 a.m. to 5 p.m. and Saturday 8 a.m. to 4 p.m., and is closed Sunday. Schedule service, see our service specials or get directions.
Adaptive cruise control FAQ
What is adaptive cruise control?
It is cruise control that also keeps a following distance. In the 2026 Ram 1500 owner's manual example, a radar sensor and forward facing camera detect a vehicle directly ahead, and ACC applies limited braking or acceleration, never above the set speed, to keep a preset distance.
Does adaptive cruise control stop the car by itself?
In the manual example it can slow to a full stop while following a vehicle. If that vehicle moves within two seconds, ACC resumes; otherwise you push RES or press the accelerator. Its braking is limited, and the driver is always responsible for braking.
What is the lowest speed I can set?
In the manual example, the minimum set speed is 20 mph. If you set ACC below 20 mph, the set speed defaults to 20 mph.
Can I use adaptive cruise control in snow or rain?
The manual example says not to use ACC in fog, heavy rain, heavy snow or sleet, or on icy, snow-covered or slippery roads.
Does adaptive cruise control see stopped cars?
No. The manual example says ACC does not react to pedestrians, oncoming vehicles or stationary objects, including a stopped vehicle in a traffic jam.
Why does my car say to wipe the front radar sensor?
In the manual example, snow, heavy rain, mud, dirt or ice can limit the radar and the system deactivates. If weather is not the cause, examine the sensor, which may need cleaning or removal of an obstruction; if the message keeps appearing with no obstruction, have the sensor realigned at an authorized dealer.
What are your service hours?
Monday to Friday 8 a.m. to 5 p.m. and Saturday 8 a.m. to 4 p.m. We are closed Sunday.
ACC warning on your dash?
Schedule service at 1200 E. Chicago St. in Elgin and tell us which message you see.
Sources
How ACC works, how it is set and cancelled, its limits and its warning messages are from the 2026 Ram 1500 Owner's Manual (publication 104308_26_DT, edition E2), used here as one manufacturer's example and read November 4, 2026. ACC equipment and operation vary by vehicle, so check your own owner's manual. Service hours are from our service page, checked the same day.
- 2026 Ram 1500 Owner's Manual (Cruise Control Systems; Adaptive Cruise Control (ACC); Precautions While Driving With ACC), Ram / Mopar, read November 4, 2026
- Service department, Elgin Auto Sales & Service Center
- Home page: address and all makes and models, Elgin Auto Sales & Service Center