How to protect your SCR and secure your DEF in cold weather

Winter is around the corner, and when temperatures drop, your selective catalytic reduction (SCR) system faces threats involving its diesel exhaust fluid (DEF). 

How to prevent DEF freezing in commercial fleets

Protecting your fleet’s DEF tanks is crucial to ensure a seamless operation during the winter months. A couple options to do so include active heating, component insulation, and regular maintenance.

Active heating

One way to avoid issues related to frozen DEF is to avoid the problem in the first place, primarily by keeping your truck warm. If possible, keep your fleet in a heated garage whenever possible to minimize the chances of DEF freezing. 

But for fleets operating in extreme climates or trucks with SCR-exposed components, aftermarket retrofits provide an added layer of protection from “flash freezing” during short stops, where the engine is turned off for an extended period. Many modern commercial trucks also often have engine-integrated heaters, but you can add one if your vehicle doesn’t. These heaters also have diesel engines, which require a higher cylinder temperature compared to gasoline vehicles. For another option, an electric block heater is an excellent solution to ensure smoother startups when freezing temperatures arrive.

Insulated heating blankets specifically engineered for DEF tanks also help ensure optimal temperatures.

Component insulation

Additionally, there are several low-cost, passive strategies for improving the efficiency of your active heating solutions. 

Adding insulated wraps to pumps and lines can slow down the rate of heat loss, keeping the DEF warmer for longer periods after the engine is shut off. This reduces the need for a full thaw cycle upon restart, saving time and energy.

But even if a fleet uses these tactics, it can be worth having back-up solutions. For example, even if a fleet uses insulated wraps to keep their system at a good temperature, they could also benefit from protective shields made of composite or metal to also protect their truck components from ice chunks and road spray.

Regular maintenance and software adjustments

Beyond having the right tools on hand to help out your truck’s SCR system, extensive SCR system checks are crucial before winter sets in, too. 

To start, technicians should verify that heating elements and insulation are functioning correctly to maintain proper diesel emissions control. To do so, make sure the system’s electrical connections are functioning and free of corrosion, and check that the sensor is working correctly. Diagnostic software can also help command the DEF heaters to activate and view the live data stream of DEF level, temperature, and quality sensor.

Beyond making sure the SCR system is working well before winter, it also helps to make sure your fleet is using quality DEF. Using DEF that is licensed by the American Petroleum Institute ensures it meets the rigorous standards required by manufacturers, and keeping it away from direct sunlight and high temperatures while it’s in storage helps make sure its ready to go when needed.

Additionally, technicians should make sure that a truck's electronic control unit (ECU) is properly updated in preparation for winter. The ECU is the brain of the entire SCR system, controlling the injection of DEF to reduce harmful emissions. It monitors engine conditions and utilizes sensors to determine the amount of DEF to inject, ensuring the system efficiently converts nitrogen oxides into harmless water and gas. Many engine manufacturers periodically release software updates or cold-weather calibrations that can enhance the engine’s warmup strategy and prevent winter-related issues down the line.

Every strategy discussed is an investment that protects you from costly downtime, financial losses, penalty fees and operational inefficiencies. To avoid DEF freezing, conduct quarterly inspections and functionality checks, verify warmup strategies with your dealer or maintenance team, and invest in insulation solutions to future-proof your fleet against cold weather.