U.S. safety regulators are investigating complaints that the autonomous braking system on newer Jeep Grand Cherokees can come on for no reason, increasing the risk of rear-end crashes.
The National Highway Traffic Safety Administration, which posted notice of the probe on Friday, said it covers about 20,000 Grand Cherokees from the 2014 model year.
The Jeeps are equipped with cruise control systems that automatically brake if they're closing too fast on an object in front of them. The safety feature, often called adaptive cruise control or automatic emergency braking, uses cameras and radar to spot cars and other objects and a computer to automatically brake to avoid a collision.
The feature is available on many high-end and even mainstream cars and is an important step in the march toward self-driving vehicles. It also is being championed by safety advocates as a breakthrough in reducing crashes and highway deaths because it can react faster than humans. But the investigation shows that the systems also can experience problems.
NHTSA says it has received nine complaints that the Jeep system suddenly reduced speed "with no pending threats in the line of travel." No crashes or injuries have been reported to the agency.
The agency says it will investigate how often the problem happens and its consequences. The probe could lead to a recall.
Several of those who complained to NHTSA said the brakes came on and nearly caused other cars to hit them from behind. Many reported that the malfunction happened multiple times.
"I can be the only vehicle on the road and this will occur. Has been happening intermittently each and every day the vehicle is driven," one owner wrote in a complaint. "Sudden unexpected stopping and unsafe performance of the vehicle putting the vehicle occupants at grave risk."
Grand Cherokee owners who experience problems should contact their dealerships for service, company spokesman Eric Mayne said in an email. Owners have the option of deactivating the automatic braking system, he said.
Several complainants wrote that dealers were unable to duplicate or fix the problem. One reported that a Grand Cherokee registered 57 diagnostic trouble codes when technicians analyzed its computer system. Complainants are not identified in the NHTSA database.
"I was driving on the freeway going 65 mph with no cars around me or in sight," another person wrote. "All of the sudden the car dashboard said Brake! And the car applied the ABS brakes and abruptly slowed the car down to 40 mph! I was so scared at that point."
Jeep maker Fiat Chrysler, also known as FCA US LLC, said its vehicles meet all federal safety standards and it's cooperating in the investigation.
The company has been feuding with NHTSA for the past year, with the agency scheduling a rare public hearing for July 2 to examine Fiat Chrysler's execution of 20 different recalls. The company says it has changed procedures and is cooperating, so the public hearing isn't necessary.