Daimler updates software on 330,000 trucks to end 5 MPH DEF ‘limp mode’

Daimler Truck North America LLC (DTNA) issued a software update for hundreds of thousands of in-service commercial trucks in order to comply with new federal guidelines regarding Diesel Exhaust Fluid (DEF) inducements.

On June 18, 2026 DTNA announced that software updates were rolled out to approximately 330,000 in-service vehicles with DD15 engines (model years 2021-2025) and DD13 engines (model years 2022-2025) since February, with updates to continue through 2026.

The software updates increase the speed limit in DEF inducements from 5 m.p.h. to 25 m.p.h., and the time to reach final inducement for component-related issues has been extended.

“This gives operators more time to complete repairs while helping minimize unnecessary downtime. Emissions compliance remains mandatory, and vehicles must still be repaired to ensure environmental standards are met. The logic to trigger final inducements related to DEF tank level remains unchanged,” the DTNA said.

The latest Freightliner and Western Star vehicles equipped with Detroit engines are already shipping with the updated software, company officials said.

DTNA is rolling out the software updates in order to comply with U.S. Environmental Protection Agency (EPA) guidance issued in August 2025 meant to provide relief for truckers and farmers from the sudden speed and power loss (also known as “limp mode”) that occurs when DEF runs out or a system sensor fails.

“For too long, small businesses like farmers, truckers, and construction workers have borne the cost of unreliable DEF systems through expensive repairs and needless downtime. This is why the SBA has been calling on OEMs to implement recent EPA guidance. The SBA welcomes Daimler Truck North America’s decision to equip vehicles with updated DEF inducement software, a common-sense step that gives operators greater reliability while reducing costs. This is exactly the kind of relief that the hardest working Americans deserve,” said U.S. Small Business Administration (SBA) Administrator Kelly Loeffler.