THINK TWICE

The 6.7L Power Stroke's most catastrophic failure is its Bosch CP4.2 high-pressure fuel pump. The CP4 can self-destruct with no warning, and when it does it drives metal debris through the entire fuel system -- injectors, rails, lines, and tank -- turning a pump failure into a whole-fuel-system replacement that commonly runs 8,000 to 12,000 dollars. Owners describe the engine dying at highway speed with total loss of power (and with it, power steering and power brakes) and refusing to restart; dealers report metal shavings in the fuel filter and a disintegrated pump. Ford never recalled the CP4, so there is no free fix -- the loss falls on the owner.

Check — Ask whether the truck still runs the original CP4 or has had a CP4 failure/replacement, and whether a disaster-prevention bypass kit is fitted; metal glitter in a fuel sample or a cut-open filter is a red flag. Budget for the risk on any unmodified high-mileage 6.7L.

Beyond the CP4, the 6.7L's biggest running headache is its emissions aftertreatment -- the DPF, EGR, and SCR/DEF (diesel exhaust fluid) system. Complaint texts across 2011-2019 describe check-engine lights and reduced-power "limp" mode traced to the diesel particulate filter or EGR, forced or failed regenerations that shudder the truck, exhaust-fluid (DEF) system faults, and even exhaust/particulate fumes entering the cabin. These are driveability and cost problems more than crash-safety defects, but they are frequent and the repairs (DPF, EGR cooler, DEF injector and sensors) are not cheap.

Check — Scan for stored emissions/DPF/EGR/DEF codes, ask about limp-mode events and regeneration behavior, and check for a "delete"/tune (illegal, and a smog/registration problem) as well as records of DPF or EGR-cooler replacement.