Topping Off Diesel Exhaust Fluid

Diesel Exhaust Fluid (DEF) is required to maintain normal vehicle operation and emissions compliance on 2010-2017 Express and Savana; 2011-2017 Silverado and Sierra 2500-3500 HD; 2014-2015, 2017 Cruze; and 2016-2017 Colorado and Canyon models equipped with a diesel engine (RPOs L5P, LML, LGH, LUZ, LWN, LH7). DEF usage will vary depending on driving style, trailer towing, loaded vehicle weight, weather, idle time and PTO use. It’s recommended to refill the DEF tank at the first opportunity after a low warning message in order to avoid any vehicle speed limitations.


Below OK Level


The DEF level indicator is displayed on the Driver Information Center (DIC) along with a series of messages regarding the amount of DEF that is available. Typically, when the DIC shows the DEF to be at any level below OK (Fig. 1), at least 2.5 gallons (9.5 L) can be added to the DEF tank (this has not yet been verified on the 2017 Cruze). The amount needed to top off the tank will vary.


F01 DEF level

Fig. 1


DEF has a shelf life of two years. However, this can be reduced if the fluid is exposed to direct sunlight or temperatures above 86°F (30°C) for sustained periods. All DEF packaging is labeled with a production date.


Filling the Tank


The DEF fill location, identified by the blue fill cap, is different on several models:

• 2010-2017 Express, Savana; 2016-2017 Colorado, Canyon; 2017 Cruze – Behind the fuel fill door
• 2014-2015 Cruze – Under the trunk floor
• 2011-2017 Silverado, Sierra – Underhood (Fig. 2)


F02 DEF fill

Fig. 2


TIP: After filling the DEF tank – unless the DEF tank was empty and the Exhaust Fluid Empty message was displayed – there may be a short delay (several miles/km) before the increased level of fluid is detected and the DIC is updated.


Typically, DEF warning messages on the DIC begin once the estimated range falls below 1,000 miles (1,609 km). When the DIC displays 1,000 miles or less, a 2.5 gallon (9.5 L)  container of DEF can be added to the tank. DEF fluid range will vary based on environmental conditions and vehicle use. To eliminate the DEF warnings, once the range drops below 300 miles (482 km), the DEF tank should be refilled.


If the vehicle speed has been limited and DEF has been added, it may take up to 30 seconds after starting the engine with the vehicle stopped for the Exhaust Fluid Empty Refill Now message to clear. If the vehicle is driven prior to the DIC message clearing, the vehicle speed will still be limited. If the DIC message clears while driving, the speed limitation will be removed gradually.


On diesel models equipped with RPOs L5P, LH7 or LWN, a Service Emission System message may display on the DIC after filling the DEF tank with the ignition on. This message may appear when using a mobile fill cart with an automatic nozzle or filling up at a commercial truck service station with DEF dispensing equipment. DTC P206B (Reductant Quality Sensor Circuit Performance) may be set. Some DEF filling equipment use pumps that create a high level of temporary aeration of the DEF fluid, which temporarily affects the operation of the in-tank DEF quality sensor. After the aeration quickly dissipates, the sensor will return to normal operation. However, if the ignition is on, the DIC message may be displayed. The ignition should be kept on until the Service Emission System message clears.


DEF in Cold Weather


DEF freezes when exposed to temperatures below 12°F (-11°C). In cold conditions, it is normal for DEF to freeze. The tank and delivery lines are heated to thaw frozen DEF.


When filling the tank in cold conditions, the vehicle may not recognize the new fluid level until the tank thaws. In certain cold conditions, it is possible to find some frozen DEF in the DEF fill pipe opening. When driving in extremely cold areas, it is recommended to fill the DEF tank prior to cold temperature exposure.


– Thanks to Larry Yaw


Updated February 24, 2017

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