CARB Low NOx Rule Will Require “Clean Idle” Engine Labels On January 1, 2024

Nov 16, 2023


In September of 2021, the California Air Resources Board (CARB) adopted the amended Omnibus Low NOx regulation which established more stringent NOx and Particulate Matter standards applicable to new 2024 and later Model Year medium- and heavy-duty diesel engines. Warranty and useful life periods were also lengthened.

The Omnibus Low NOx rule first promulgated in 2002 and amended several times over the past 21 years, including the 2021 version which is taking effect on January 1, 2024. It applies to medium-duty engines (used in vehicles from 10,001 to 14,000 pounds GVWR) and heavy-duty engines (used in vehicles over 14,000 pounds GVWR). This will cover nearly all Class A diesel motorhomes, as well as many Class Cs and even some Class Bs.

In 2008, provisions were added to the regulation to require all heavy-duty engines to meet a new engine idling standard, which could be met by use of an Engine Shutdown System or by meeting an optional Clean Idle Emission Standard. The new provisions also required labels to be attached to any heavy-duty vehicle which has an engine certified to the Clean Idle emissions standard in the regulation, or which had a certified auxiliary power source. An exemption from the idling requirements for heavy-duty engines in RVs was included in those 2008 provisions.

Why it Matters Now

As part of the new regulation, the engine idling provisions were extended to medium-duty engines. However, the exemption from the engine idling standards and the labeling of heavy-duty diesel motor home engines that the RV industry enjoyed for the past 15 years was removed. As of January 1, 2024, all 2024 and later model year heavy-duty diesel engines installed in motor homes must be labeled to show they meet the Clean Idle provisions of the regulation in 13 CCR section 1956.8(a)(2)(C)3 or that they have a certified Auxiliary Power System pursuant to 13 CCR 2485(c)(3)(A). For 2024, 2025 and 2026 model year heavy-duty diesel engines certified to the provisions specified, the label must contain the following statement: “This legacy engine is certified under the provisions of 13 CCR 1956.8(a)(2)(C)3 applicable to XXXX model year."

For 2024 through 2026 model year heavy-duty diesel engines rated at or above 525 bhp maximum power and certified to the provisions specified in 13 CCR section 1956.8(a)(2)(C)2, the label must contain the following statement: “This engine conforms to the 525 horsepower and above exemption specified in 13 CCR 1956.8(a)(2)(C)2 applicable to XXXX model year."

Failure to have the proper engine labels will result in the motorhome not being able to be registered in California. As such, this would impact consumers, RV dealers, and manufacturers alike.

Engine manufacturers are well aware of this new requirement and should be installing the labels on 2024 model year and after heavy-duty diesel engines destined for California. RV manufacturers should be making certain that any heavy-duty diesel engine-equipped motorhome being shipped to California has the required labels attached. RV dealers should be certain that any diesel motorhome being sold by their dealership contains the needed labels if the engine is from model year 2024 or later. This will avoid the consumer having any issues with titling and registration.

For further information, please contact Michael Ochs, RV Industry Association Director of State Government Affairs, at 571-665-5860 or