Senators target cold-weather truck shutdowns

WASHINGTON — New legislation has been introduced aimed at preventing automatic engine derate or shutdown functions that can be triggered in trucks operating in prolonged cold weather.

A copy of the legislation, introduced last week by Sens. Dan Sullivan, R-Alaska, and Cynthia Lummis, R-Wyo., was not immediately available.

According to the bill’s summary, it would “require the administrator of the Environmental Protection Agency to authorize manufacturers of certain vehicles to suspend engine derate or shutdown functions in prolonged cold weather conditions, and for other purposes.”

Such derate and shutdown functions are related primarily to Diesel Exhaust Fluid (DEF) and Selective Catalytic Reduction systems used by truck manufacturers to meet EPA emissions standards.

Unexpected derates can reduce a truck’s speed and power, leaving trucks stranded due to system faults or low DEF, which in turn can lead to costly maintenance and supply chain delays.

The bill represents a potential push to codify and expand guidance issued by EPA in August to ensure that existing diesel trucks, which use DEF to reduce nitrous oxide emissions, do not experience sudden engine failures after running out of the fluid.

According to EPA’s new guidelines, starting with model year 2027, all new diesel on-road trucks must be engineered to avoid sudden power loss and resulting derates after running out of DEF.

Under the new guidance, a warning light appears for 650 miles after a fault is detected, with only gradual engine derates occurring over a total of 8,400 miles or 160 hours, ending with the engine slowing to 25 mph. The changes are expected to give truck drivers much more time to diagnose and fix system problems.