Starting in 2012, Union Pacific sent 28 SD60Ms to EMD for a rebuild program. Called SD32ECOs by EMD, the program replaced the existing 710G3A V16 prime mover with an EPA Tier-II-compliant 710G3B-T2 turbocharged V12, with electronic fuel injection. The Union Pacific SD60M car body retained many of its major components and subassemblies, having them recycled and recertified as equal to new. EMD also installed a completely new control system which is adaptable to both minimum emissions and minimum fuel consumption modes, depending upon the specific locomotives assignment. Classified as an SD59M-2 by the Union Pacific Railroad, unit numbers 9900-9927 are currently at work on the system.
Recently rebuilt, these newly designated SD59M-2's are frequently spotted on western rails where their low emissions and fuel economy is favored.