Technical Service Bulletin 25-007-24 — 2021 RAM 4500

"Diesel Exhaust Fluid (DEF) Fluid Freezing Customers must experience a Malfunction Indicator Lamp (MIL) illumination and the vehicle must exhibit/set the following Diagnostic Trouble Code (DTC): ● P203E-00 - Reductant Level Sensor 1 Circuit Intermittent-Erratic. Customers may also experience one or more of the following: ● Repeated freeze/thaw cycles of the urea tank to cause solid DEF crystals to form and settle on the focus tube, blocking the level sensor signal. ● Rapid temperature swings from below freezing to above freezing causing an incomplete thaw of the DEF tank. When the vehicle is powered on, the diagnostic is enabled due to thawed DEF at the tank bottom surface, but the fluid in the center is still partially frozen. ● Not following the proper DEF fill procedure and overfilling the tank This bulletin involves replacing the urea delivery module and grade vent valve and updating the Dosing Control Unit (DCU) software This bulletin involves replacing the urea delivery module and possibly updating the Dosing Control Unit (DCU) software"