During the EA17-002 investigation, the agency reviewed and analyzed reports of exhaust odors in the passenger cabins of Model Year 2011 to 2017 Ford Explorers. This investigation required an approach that incorporated knowledge and expertise from the automotive, medical, environmental health, and occupational safety fields. The agency conducted an in-depth investigation that encompassed the review of over 6,500 consumer complaints, conducting field inspections, and testing the relevant vehicles, both independently and in coordination with Ford and other entities. During the investigation, the evolution of Ford service bulletins intended to reduce the level of exhaust odors and carbon monoxide (CO) entering the occupant compartment was examined and independent tests to evaluate the effectiveness of the final Field Service Actions (FSA) for both consumer and police vehicles were conducted. As part of the investigation, the agency also examined the effects of cracked exhaust mani-cats on the measured CO levels in the vehicles and tested the FSA repairs to ensure they did not adversely impact occupant compartment CO levels due to cracked mani-cats.The investigation identified upfitting issues for Police Interceptor vehicles. Upfitting (sirens, lights, cages, auxiliary power, etc.) is typically performed by governmental fleet operations, independent repair facilities, or local Ford dealers after the sale of the new vehicle. Sealing issues caused by upfitting were responsible for the highest measured carbon monoxide levels in tested vehicles. The police FSA instructs how to inspect the quality of the vehicle upfits and how to properly seal any leaks caused by these upfits, at no cost to the police agency. Similarly, the highest CO levels measured in consumer vehicles were usually traced to sealing issues caused by rear crash damage where the repairs did not ensure sealing integrity. The most recent Ford FSA procedure for both the police (17B25) and consumer vehicles (17N03) includes an HVAC reprogramming operation. Tests by Ford and NHTSA have demonstrated a substantial reduction of CO levels due solely to the HVAC reprogramming. Other FSA repairs also demonstrated measurable contributions to CO level reductions during controlled tests.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.NHTSA received thousands of reports alleging odors which triggered a variety of physiological responses, predominately nausea, headaches, and lightheadedness. NHTSA focused the investigation on accurately measuring vehicle CO levels, and accurately measuring carboxyhemoglobin (COHB) levels from properly administered blood tests. Using rigorous test methods to produce exhaust gas intrusion in vehicles with a properly performed FSA, occupant compartment CO levels remained below current environmental limits for CO in any environment (EPA ambient air quality standards). 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. This investigation finds that the 2011-2017 Ford Explorer vehicles when accurately measured produce occupant compartment CO levels which fall below current accepted health standards, and could not identify COHB levels for vehicle drivers or other occupants, which exceeded thresholds for acute physiological effects. Therefore, the agency has not identified a defect that represents an unreasonable risk to motor vehicle safety.This inve
