Diagnostic Aids

WARNING: This page is about a different car, the 2019 GMC Savana 3500, 2019 GMC Savana 2500, 2019 Chevrolet Express 3500, and 2019 Chevrolet Express 2500. However, it is still accessible from the selected car via links, so may be relevant.

Some reductant fluid (DEF) fill equipment may aerate the fluid which can temporarily affect the operation of the reductant quality sensor. A DTC may set and the Service Emission System message may display in the driver information center. The fluid aeration will quickly dissipate on its own and operation of the reductant quality sensor will return to normal. Filling the reductant fluid tank with the key off will help prevent the reductant quality sensor from being affected by this condition. The operation of the reductant quality sensor may also be affected by a concentration of reductant crystals around it that forms when reductant freezes and thaws. Agitation of the reductant during normal driving will cause the crystallized reductant to disperse and allow the sensor to return to normal operation. If the tank has been frozen, the vehicle should be parked inside overnight to allow the reductant system to warm to greater than 5°C (41°F).