The National Highway Traffic Safety Administration (NHTSA) has closed its investigation into the 2011-2017 Ford Explorer. The agency examined claims that exhaust fumes were entering the passenger compartment in both the consumer model and the Police Interceptor. However, NHTSA has ultimately determined that the automaker does not have to issue any recalls related to these complaints.

The agency pointed to two causes for the fumes: insufficient crash repairs in consumer cars and poor installation of aftermarket upfits in Police Interceptors. According to the agency’s January 17 summary, “Throughout the investigation, vehicles accurately measured with higher levels of carbon monoxide were almost always affected by upfitter alterations, damage, or other causes compromising rear passenger cabin seals.”

Gallery: 2016 Ford Explorer: Review

Police Interceptors often undergo upfitting, a process that adds sirens, lights, cages, and other equipment to vehicles for law enforcement duties and first responders. Sealing issues related to these added features “were responsible for the highest measured carbon monoxide levels in test vehicles,” said the agency’s report. It was a similar case with the consumer models, with the agency usually tracing the source of exhaust fumes to rear crash damage repairs that “did not ensure sealing integrity.” 

NHTSA studied the problem for six years, incorporating expertise from the automotive, medical, environmental health, and occupational safety fields into its investigation. The agency also conducted field inspections independently and in cooperation with Ford and other entities while reviewing over 6,500 consumer complaints.

Over the course of NHTSA’s investigation, which initially began in 2016, Ford issued Field Service Actions (FSA) for both Explorer models that led to measurable reductions in CO levels. Ford and NHTSA tested the automaker’s most recent one, which called for reprogramming the HVAC system, and saw “a substantial reduction of CO levels.” In 2017, Ford said that it’d fix Police Interceptors with aftermarket installations, checking the seals and making repairs at no cost.

The agency even went as far as performing blood tests to measure passengers’ CO levels. However, the agency concluded, “Furthermore, even without FSA repairs, no vehicles unaffected by upfitter issues or prior crash damage were identified with CO levels that exceed accepted occupational CO exposure levels.”

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