As snow, ice, or salt grime gathers on cars this winter, many of the sensors that are key to the operation of advanced safety systems can become blocked and shut down.

More on Advanced safety Systems

Take, for example, forward-collision warning (FCW) and automatic emergency braking (AEB) systems. These life-saving features rely on radar sensors that are often mounted in the car's grille—sometimes even in the car's emblem—or on its front bumpers. When these sensors can no longer tell what's in front of them, they can shut down, illuminating a warning light on the dash. At that point, the systems aren't working.

Some automakers say that to work best, AEB sensors, for example, need to sit behind the front grille, and so can be at the mercy of snow or ice build-up. Automakers say other sensors are carefully placed around the car, such as on bumpers, so they can best do their jobs.

Understanding where the sensors are located and how to keep them clear and functioning properly is important. The locations are listed in the owners manual, and the dealer can also show you on your particular vehicle. We also offer some advice near the end of this report.

Some automakers have moved key sensors to behind the windshield in an effort to shield them from the weather.

“Volvo moved all the semi-autonomous drive sensors (for FCW and AEB, among others) to an area in the windshield that falls within the wiper sweep to ensure a clear view of the road at all times,” says spokesman Russell Datz. Still, even on Volvos, parking and blind-spot sensors remain on the outside of the vehicle, where they can be affected by weather, he says.

Remember, too, that your car's safety systems may have issues properly reading lane markings in heavy snowfall or intense rainstorms, or when those marking have been altered during road work.

Mercedes-Benz E-Class warning screen.
Mercedes-Benz E-Class

Six Key Areas to Keep Clean

  • The grille: When you first get a new car, spend some time identifying all of the sensors that may be hidden in the grille area so that you’ll know where to focus your cleaning effort. Recent vehicles that have FCW, AEB, and/or adaptive cruise control most likely have their radar sensors located out front, either within the grille or in the lower center of the front bumper.
  • The windshield: More cars are using cameras and sensors behind the glass for FCW or automatic wipers. As these sensors can sometimes be located outside the path of the wipers, it’s worthwhile to stop periodically during foul weather to completely clear your windshield of built-up ice and snow.
  • Rear body quarter panels: These often house radars that are used to power blind-spot monitoring systems, or behind you when your vehicle is in Reverse. Older models (such as some from Acura and Volvo) use a camera located just below the outside mirrors.
  • Sensors in the car’s front and, often, rear bumpers: These power the parking alert systems. The front ones let you know when you’re getting too close to an object; the rear ones can tell you if a car is moving toward you in a parking lot. 
  • The rearview camera: Ice, snow, salt, and dirt can muck this up and make it useless.
  • Remember the cameras located in the front grille, underneath your side mirrors, and in the back that power a 360-degree-view system. Ice, snow, and salt can often cake on these, making them unusable.

If weather permits, get regular car washes to keep the sensors on your car clean. For do-it-yourself cleaning, use a mild automotive-specific detergent (so you won't damage your car’s paint). Be gentle in cleaning fenders, because salt and sand can be abrasive on paint.

Make sure you have a clean paper towel or rag to dry the area after cleaning. You don’t want to be part of the problem by coating the car in ice.

Make sure the entire car is snow-free before driving. It's the law in some areas. And, of course, you may have to clear the sensors several times on a trip, especially if you’re driving through a storm. One CR staffer needed to stop five times on a 100-mile trip through a snowstorm to keep his car's sensors clean. 

From the 'Consumer 101' TV Show

Today's cars come with cutting edge safety technology that can stop working with one simple thing: dirt. Consumer Reports' expert show on 'Consumer 101' where these important safety sensors are on a car and how to keep them clean.