U0401 – Invalid Data Received From ECM/PCM

What does U0401 mean?

A module received data from the engine control module (ECM/PCM) that was implausible or corrupted. Unlike U0100, communication is working — the content of the message is the problem, which usually points to a sensor feeding bad data to the ECM rather than to a network fault.

What causes U0401?

Listed from most to least common:

1. 1Faulty sensor feeding incorrect data to the ECM
2. 2Other stored ECM codes causing implausible values to be broadcast
3. 3CAN bus interference or wiring problems
4. 4Low system voltage
5. 5ECM software needing an update
6. 6Failed ECM (less common)

Code breakdown

Common symptoms

• Check engine light on, often with other module warning lights
• Transmission may shift oddly or enter limp mode
• Traction or stability control may be disabled
• Multiple seemingly unrelated codes stored

How to diagnose

1. 1Read codes from every module, not just the engine. U0401 is a symptom; the cause is usually another stored code.
2. 2Diagnose and repair engine sensor codes first — the invalid data usually originates there.
3. 3Check battery voltage and charging system.
4. 4Inspect CAN bus wiring for damage or interference.
5. 5Check whether the ECM has an available software update, since some cases are resolved by reflashing.
6. 6Clear codes after repairs and verify whether U0401 returns.

Behavior depends on which data is invalid. Transmission shifting and stability systems may be affected. Diagnose the underlying sensor codes rather than the U-code itself.

Common fixes and estimated costs

Costs are rough US estimates including parts and labor. Actual pricing varies significantly by vehicle, region, and shop rates.

Good to know

Treat U0401 as a pointer, not a diagnosis. Fixing the sensor or circuit codes that caused the ECM to broadcast bad data almost always clears this code as well.

Related codes