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U1601 on the 2021 Ram 3500

The bulletins listed name this code in NHTSA's summary, or are about the same components. A bulletin or a recall listed here may apply to the model year. None of it is a diagnosis.

This code is specific to a manufacturer and is not described here. Its meaning is in the manufacturer's service information.

Bulletins for this model year that name U1601
S2008000186 REV.B2024-12-21. Service bulletin. Engine Control Module (ECM) Flash Failure, Diagnostic Trouble Code (DTC) U1601 – ECU Application Software Code 1 Missing Or Corrupted
S2008000186REVA2023-01-09. Service bulletin. Engine Control Module (ECM) Flash Failure, Diagnostic Trouble Code (DTC) U1601 ? ECU Application Software Code 1 Missing Or Corrupted
S20080001862022-10-17. Service bulletin. Engine Control Module (ECM) Flash Failure, Diagnostic Trouble Code (DTC) U1601 ? ECU Application Software Code 1 Missing Or Corrupted
S20080001862020-12-21. Service bulletin. Engine Control Module (ECM) Flash Failure, Diagnostic Trouble Code (DTC) U1601 ? ECU Application Software Code 1 Missing Or Corrupted

4 on file from NHTSA, as of 2026-10-19. See them in the bulletin list. A bulletin lists model years: read the document for which vehicles it concerns.