In a report from Green Car Congress, they briefly explain that CARB has been working with Cummins on a solution to this problem. It’s not a defeat device, the vehicles were in fact perfectly clean when new, but the catalysts that reduce the emissions to legal levels were not aging well and eventually caused excess emissions of NOx (as always, the one big bugaboo for diesels—on everything else they’re quite clean while equipped with DPFs).

Satisfied that the longevity of updated components is sufficient, there is now a recall in place to remove the poorly aging catalysts and install longer lived units.


Some have commented that it seems next to impossible for diesels to meet emissions reliably and maybe the technology should be abandoned altogether. But to some of us with more experience in the field and with how manufacturers operate to obtain feedback from technicians and analyze failed parts, I would argue it’s more akin to the early smog days with gasoline engines before 3 way catalysts and electronic fuel injection with a feedback loop.

This is simply new technology that needs time to mature and get better in every regard and the only way to get there is continual, massive investment in R&D and time to allow technologies to mature and have better feedback on their effectiveness and longevity in real world conditions over the long term. At the end of the day, battery electrics will not be able to provide everyone on the scale we currently have using internal combustion. At least not for some time to come yet. More efficient internal combustion processes like diesel will be needed in the interim. And, as some CARB officials have pointed out, they in fact like diesels—when they meet their tough regulations. Aside from the NOx bugger, they’re cleaner than gas engines. Less soot, less carbon monoxide, less hydrocarbon emissions, less CO2 because of their increased efficiency (NOTE: CO2 is not a harmful gas, we in fact trade off for having more CO2 from tailpipes to improve air quality with most catalytic processes, it’s just that CO2 is a big reason why we have climate change).


Here’s to hoping manufacturers can make emissions equipment live up to the “million mile engine” reputation diesel engines tend to have.

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