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U0400

Code meaning and manufacturer information

OBD-II / DTC

Reference meaning

What does this code mean?

The wording below belongs to the named make and communication. Match the complete code, reporting module, model year and engine before applying it.

A code identifies a detected condition, not a part that must automatically be replaced.

Narrow by vehicle

A listed vehicle is a research lead. Confirm the engine, production range and software in the manufacturer's information.

Before replacing a part

Record codes and freeze-frame data. Check battery condition, related codes and visible wiring or hose damage. Follow the vehicle's diagnostic procedure and test results before replacing parts.

Scan worksheet →

Manufacturer communications

1

Original wording in English

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M1720 ↗

HARLEY-DAVIDSON

SERVICE BULLETIN M1720 (REV A): PAN AMERICA ELECTRONIC CONTROL MODULE (ECM) UPDATE. PURPOSE: Initial release 3/3/2026. Revision A. 3/30/2026. Updated: Purpose for Service Bulletin and Required Dealer Action. Adjust information for 2024 models. Purpose for Service Bulletin. This bulletin informs dealers that there is an Electroni…

Check vehicle applicability

12

A listed vehicle is a research lead. Confirm the engine, production range and software in the manufacturer's information.

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MakeModelModel year
Harley-DavidsonRA1250 ↗2024
Harley-DavidsonRA1250 ↗2023
Harley-DavidsonRA1250 ↗2022
Harley-DavidsonRA1250 ↗2021
Harley-DavidsonRA1250S ↗2025
Harley-DavidsonRA1250S ↗2024
Harley-DavidsonRA1250S ↗2023
Harley-DavidsonRA1250S ↗2022

Can I keep driving?

A code alone cannot establish whether driving is safe. A flashing malfunction light, severe shaking, overheating, oil-pressure warning or loss of braking or steering needs prompt attention. Stop in a safe place and seek assistance when control or engine safety is affected. Follow the vehicle handbook.