Exhaust System Emission Control Urea Injection System (def) problems of the 2021 Chevrolet Silverado 1500

The contact owns a 2021 Chevrolet Silverado 1500. The contact stated that while driving approximately 65 mph, the message "service def system" was displayed and the check engine warning was illuminated. The message speed would reduce by increments of 10 to 15 mph until the vehicle could not accelerate 5 mph after driving 75 miles. The contact stated that a handheld scanner was used to retrieve dtc: p20b9. The contact stated that the failure was a recurring failure. The vehicle was taken to a local dealer where it was diagnosed and determined that the def tank heater module needed to be replaced. The contact stated that the dealer was aware of TSB: 21-na-002 and 22-na-150; however, the vehicle had a salvage title and was not eligible for the repairs. The manufacturer was informed of the failure and referred the contact to the NHTSA hotline for assistance. The failure mileage was approximately 53,400.