Spectra Premium Diesel Exhaust Fluid Heaters Features A Precisely Calibrated Heater And Temperature Sensor To Ensure The Def Does Not Freeze During Normal Vehicle Operation The Def Heater Also Provides A Reliable And Accurate Fluid Level Indicator To Ensure The Tank Is Not Depleted Of Def, Which Can Consequently Illuminate The Check Engine Light And Limit The Vehicle's Operating Speed Heaters Are Validated By Our In-House Team Of Canadian Engineers Ensuring It Meets Oe Requirements