Deutz to change SCR strategy for off-highway engines

Deutz is to introduce a new strategy for selective catalytic reduction (SCR) systems in off-highway engines. The changes will be implemented as a software update for engines in the field and on all new engines.

The change follows revised guidelines issued by the US EPA (IACD-2025-10). This addresses feedback from customers who were affected by sudden power reductions when problems occurred with the SCR system.

Deutz TCD 3.9/4.0 with emissions aftertreatment system (Photo: Deutz)

Possible causes for the issue include low levels of DEF (diesel exhaust fluid, or urea) or low DEF quality. Deutz also notes that the issue could be caused by tampering with the system.

The change will be useful for machine OEMs looking to market machines in as many regions as possible without the need for region-specific settings. The new strategy will deliver a ‘harmonized SCR inducement strategy with a US/EU dual label.

New engines with US/EU dual certification, as well as revised engines with Tier 4 emissions standards will respond significantly less severely, particularly in cases involving DEF quality issues and tampering.

In certain cases, time until final inducement may be extended from the previous four hours to as much as 100 hours. The ‘forced idle’ previously required for the US Tier 4 standard will no longer apply, giving operators more time to remedy the cause in a controlled manner, while continuing their work.