Diagnostic Overview
Mack fault code U010E00 usually indicates lost communication with the reductant control module or DEF control system. When the ECM cannot communicate with the DEF module, SCR dosing may be disabled and the truck may enter warning or derate logic. Communication faults should be diagnosed electrically before replacing DEF components.
Likely Causes
Failed DEF/reductant control module; power or ground loss; CAN wiring fault; connector corrosion; blown fuse; low battery voltage.
What To Check First
Check module power and ground, fuses, CAN wiring, connector condition, and network communication before replacing the reductant module.