U0401 on Mazda vehicles The data arriving from the engine control module is not valid

A model year is listed because the code is named in its own record — a bulletin filed against it, or an owner’s complaint about it — not because every one of these vehicles sets it. Counts are documents in NHTSA’s files, not failure rates.

Bulletins and campaigns Mazda filed with NHTSA whose summary names U0401. Quote the document number at the service desk — it is a diagnosis the maker has already written down.

• 01-015-18-3513a Service bulletin
  2018-10-23 · Engine
• Some vehicles may experience a lack of power and the check engine light on with DTC P061B:00 and U0401:00 stored in the PCM memory when engine cranking is interrupted and on A/T vehicles, DTC U0442:00 is also stored. This concern most likely occurs when the brake pedal is released during engine cranking. DTC P061B:00 - [PCM] Internal control module torque calculation performance problem. DTC U0401
• SA-011-19 Service bulletin
  2019-02-28 · Power Train
• Some vehicles may display some (or all) of the following symptoms: Check engine light on wit DTC P061B, Surging on acceleration, Transmission will not shift past 4th gear, Various U codes (U0401 ABS, U0401, U0415 FSC, U0301, U0316 SBS/MRCC, U0442 TCM) may be set.
• SA-011-19a Service bulletin
  2019-05-13 · Power Train
• Some vehicles may display some (or all) of the following symptoms: Check engine light on wit DTC P061B Surging on acceleration Transmission will not shift past 4th gear Various U codes (U0401 ABS, U0401, U0415 FSC, U0301, U0316 SBS/MRCC, U0442 TCM) may be set
• 01-009-17-3377a Service bulletin
  2017-12-22 · Power Train — Automatic Transmission — Control Module (Tcm/Pcm/Tecm)
• Some customers may experience a lack of power when driving. The master warning light or the check engine light turns on and DTC P130C:00 and U0401:00 (ABS) stored in memory. It occurs mostly at low temperatures. Once the ignition is turned off and on, the concern may disappear. NOTE: DTC P130C:00 may not be found upon M-MDS self test since this DTC is detected when the condition occurs in two dri
• 01-010-18-3442 Service bulletin
  2018-03-29 · Engine
• Some vehicles may exhibit an engine misfire during acceleration with the check engine light flashing and the following DTC(s). P0302:00 - Cylinder No.2 misfire detected and/or P0303:00 - Cylinder No.3 misfire detected. NOTE: Even if a misfire occurred, the DTCs may not be stored because they are set after the continuous misfire occurred for 2 drive cycles. In this case, check if the following info
• 01-010-18-3442a Service bulletin
  2018-04-27 · Engine And Engine Cooling
• Some vehicles may exhibit an engine misfire during acceleration with the check engine light flashing and the following DTC(s). P0302:00 - Cylinder No.2 misfire detected and/or P0303:00 - Cylinder No.3 misfire detected NOTE: Even if a misfire occurred, the DTCs may not be stored because they are set after the continuous misfire occurred for 2 drive cycles. In this case, check if the following infor
• 01-010-18-3442b Service bulletin
  2018-07-30 · Engine
• Some vehicles may exhibit an engine misfire during acceleration with the check engine light flashing and the following DTC(s). P0302:00 - Cylinder No.2 misfire detected and/or P0303:00 - Cylinder No.3 misfire detected NOTE: Even if a misfire occurred, the DTCs may not be stored because they are set after the continuous misfire occurred for 2 drive cycles. In this case, check if the following infor
• SA-011-26 Service bulletin
  2026-02-26 · Engine
• Some vehicles may display some (or all) of the following symptoms: • Check engine light on with DTC P061B • Light increase in engine rpms during acceleration • Transmission will not shift past 4th gear • Various U codes (U0401 ABS, U0401, U0415 FSC, U0301, U0316 SBS/MRCC, U0442 TCM) may be set
• SA-008-20 Service bulletin
  2020-01-10 · Service Brakes
• INSTRUMENT CLUSTER WARNING MESSAGE "SAFETY AND DRIVER SUPPORT SYSTEMS PARTIALLY DISABLED" AND DTC U0401:68 IS STORED:Some customers may experience an instrument cluster warning message "Safety and Driver Support Systems Partially Disabled" and DTC U0401:68 [VEHICLE CONTROL MODULE (US)] (Error signal received from PCM, DSC HU/CM, instrument cluster, or body control module (BCM)) stored. This may be
• SA-037-21 Service bulletin
  2021-05-24 · Service Brakes
• Some customers may experience an instrument cluster warning message "Safety and Driver Support Systems Partially Disabled" and DTC U0401:68 [VEHICLE CONTROL MODULE (US)] (Error signal received from PCM, DSC HU/CM, instrument cluster, or body control module (BCM)) stored. This may be caused by the customer riding the brake pedal.

A stored code names the test that failed, never the part that caused it. The record above is what Mazda and its owners have filed about it; the code’s page across every make has the whole file.