The National Highway Traffic Safety Administration has broadened its probe into reports that 2011-2017 model year Ford Explorers are experiencing leaks in their exhaust systems, which could cause carbon monoxide to enter the vehicle’s cabin. There's a risk that intruding gases could make drivers ill or even lose consciousness.

According to NHTSA, the expanded investigation now involves a total of 1.3 million Explorer SUVs, including the Police Interceptor version that's marketed and sold directly to law-enforcement agencies. More than 2,700 complaints have been filed with Ford and NHTSA, with three reported crashes along with 41 injuries. There have been no reported fatalities, it says.

The NHTSA report states that symptoms resulting from these possible exhaust leaks can include nausea and headaches. In some instances, however, the driver reported a loss of consciousness, leading to an accident and injury. NHTSA’s ongoing investigation has found that two accidents have involved police departments, both with the Police Interceptor version of the Explorer.

It says that small cracks in the exhaust manifold, specifically in these Police Interceptor models, could be leading to reports of exhaust odors in the vehicle’s cabin.

This year-long investigation has officially been upgraded by NHTSA to an “engineering analysis,” which is one step away from a full recall notice.

"Safety is our top priority," a Ford spokeswoman, Elizabeth Weigandt, said in an email Friday. "A dedicated Ford team is working with police customers, police-equipment installers, Police Advisory Board members, and NHTSA to investigate reported issues and solve them. Customers with concerns about Explorers and Police Interceptor Utilities can call our dedicated hotline at 888-260-5575 or visit their local Ford dealership."

Ford has already issued service bulletins to its dealerships about this problem. If customers have a concern about their own Explorer, they should bring the car to the dealership and mention Service Bulletin TSB 14-0130. This bulletin instructs dealers on possible repairs, and covers the 2011-2015 model years; NHTSA's new investigation extends the model years through 2017 models.  

"We're pleased to see NHTSA intensify its investigation," says William Wallace, a policy analyst for Consumers Union, the policy and mobilization arm of Consumer Reports. "We urge the agency to get to the bottom of this issue expeditiously."

In Consumer Report’s annual Auto Reliability Survey, eight owners mentioned the problem of exhaust fumes in the cabin of their Ford Explorer SUV. The vehicles, which ranged from 2013 to 2017 model years, all fall within the current NHTSA engineering study.

One owner of a 2017 Explorer said in the survey, “If you accelerate over 3,500 rpm, the cabin smells like rotten eggs—terrible. Will take it to the dealer next week.” An owner of a 2016 Explorer noted, “Vehicle gets exhaust smell through A/C into cabin when hard-accelerating.”