DD15 emissions system maintenance

[Colter]

The most common Detroit aftertreatment fault is Nox conversion efficiency too low, without spending copious amounts of money on a laptop + link + software the next best tool would be the Nexiq Bluetooth mini or something like that, you can read everything but cant clear anything.

Sensor failures are not as common as wiring issues in the DD engines but many times you see sensors blindly thrown at an issue. Repetitive sensor failures (temp, Nox, etc) can be EGR cooler failure which is checked by removing and inspecting EGR piping for coolant .

Nox conversion codes rarely are a sensor issue but more likely DEF filter breakdown and system restrictions due to material floating around. There is a RS Service kit for the Detroit's, (sometimes conversion codes need a new pump and/or injector as well) its about a 3-8 hour ordeal to replace screens and filters in the RS kit. Not a bad thing to do every once in a while or simply once and then REPLACE DEF FILTERS ANNUALLY (regardless of engine make )

The conversion code issue is pure speculation but is the most common issue seen on them and miserable to solve as they will almost always pass the tests while stationary and reoccur once under load.