Apps that remotely track and control cars are being weaponized by abusive partners. Car manufacturers have been slow to respond, according to victims and experts.

After almost 10 years of marriage, Christine Dowdall wanted out. Her husband was no longer the charming man she had fallen in love with. He had become narcissistic, abusive and unfaithful, she said. After one of their fights turned violent in September 2022, Ms. Dowdall, a real estate agent, fled their home in Covington, La., driving her Mercedes-Benz C300 sedan to her daughter’s house near Shreveport, five hours away. She filed a domestic abuse report with the police two days later.

Her husband, a Drug Enforcement Administration agent, didn’t want to let her go. He called her repeatedly, she said, first pleading with her to return, and then threatening her. She stopped responding to him, she said, even though he texted and called her hundreds of times.

Ms. Dowdall, 59, started occasionally seeing a strange new message on the display in her Mercedes, about a location-based service called “mbrace.” The second time it happened, she took a photograph and searched for the name online.

“I realized, oh my God, that’s him tracking me,” Ms. Dowdall said.

“Mbrace” was part of “Mercedes me” — a suite of connected services for the car, accessible via a smartphone app. Ms. Dowdall had only ever used the Mercedes Me app to make auto loan payments. She hadn’t realized that the service could also be used to track the car’s location. One night, when she visited a male friend’s home, her husband sent the man a message with a thumbs-up emoji. A nearby camera captured his car driving in the area, according to the detective who worked on her case.

Ms. Dowdall called Mercedes customer service repeatedly to try to remove her husband’s digital access to the car, but the loan and title were in his name, a decision the couple had made because he had a better credit score than hers. Even though she was making the payments, had a restraining order against her husband and had been granted sole use of the car during divorce proceedings, Mercedes representatives told her that her husband was the customer so he would be able to keep his access. There was no button she could press to take away the app’s connection to the vehicle.

“This is not the first time that I’ve heard something like this,” one of the representatives told Ms. Dowdall.

A spokeswoman for Mercedes-Benz said the company did not comment on “individual customer matters.”

A car, to its driver, can feel like a sanctuary. A place to sing favorite songs off key, to cry, to vent or to drive somewhere no one knows you’re going.

But in truth, there are few places in our lives less private.

Modern cars have been called “smartphones with wheels” because they are internet-connected and have myriad methods of data collection, from cameras and seat weight sensors to records of how hard you brake and corner. Most drivers don’t realize how much information their cars are collecting and who has access to it, said Jen Caltrider, a privacy researcher at Mozilla who reviewed the privacy policies of more than 25 car brands and found surprising disclosures, such as Nissan saying it might collect information about “sexual activity.”

“People think their car is private,” Ms. Caltrider said. “With a computer, you know where the camera is and you can put tape over it. Once you’ve bought a car and you find it is bad at privacy, what are you supposed to do?”

Privacy advocates are concerned by how car companies are using and sharing consumers’ data — with insurance companies, for example — and drivers’ inability to turn the data collection off. California’s privacy regulator is investigating the auto industry.

For car owners, the upside of this data-palooza has come in the form of smartphone apps that allow them to check a car’s location when, say, they forget where it is parked; to lock and unlock the vehicle remotely; and to turn it on or off. Some apps can even remotely set the car’s climate controls, make the horn honk or turn on its lights. After setting up the app, the car’s owner can grant access to a limited number of other drivers.

Domestic violence experts say that these convenience features are being weaponized in abusive relationships, and that car makers have not been willing to assist victims. This is particularly complicated when the victim is a co-owner of the car, or not named on the title.

Detective Kelly Downey of the Bossier Parish Sheriff’s Office, who investigated Ms. Dowdall’s husband for stalking, also reached out to Mercedes more than a dozen times to no avail, she said. She had previously dealt with another case of harassment via a connected car app — a woman whose husband would turn on her Lexus while it sat in the garage in the middle of the night. In that case, too, Detective Downey was unable to get the car company to turn off the husband’s access; the victim sold her car.

“Automobile manufacturers have to create a way for us to stop it,” Detective Downey said. “Technology may be our godsend, but it’s also very scary because it could hurt you.”

Mercedes also failed to respond to a search warrant, Detective Downey said. She instead found evidence that the husband was using the Mercedes Me app by obtaining records of his internet activity.

Unable to get help from Mercedes, Ms. Dowdall took her car to an independent mechanic this year and paid $400 to disable the remote tracking. This also disabled the car’s navigation system and its S.O.S. button, a tool to get help in an emergency.

“I didn’t care. I just didn’t want him to know where I was,” said Ms. Dowdall, whose husband died by suicide last month. “Car manufacturers should give the ability to turn this tracking off.”

Eva Galperin, an expert on tech-enabled domestic abuse at the digital rights group Electronic Frontier Foundation, said that she has seen another case of an abuser using a car app to track a victim’s movements, and that the victim didn’t realize it because she “isn’t the one who has set it up.”

“As far as I know, there are not any guides for how to lock your partner out of your car after you break up,” Ms. Galperin said.

Controlling partners have tracked their victims’ cars in the past using GPS devices and Apple AirTags, Ms. Galperin said, but connected car apps offer new opportunities for harassment.