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U0401 – Invalid Data Received From ECM/PCM A (OBD2)

U0401 means "Invalid Data Received From ECM/PCM A". An "invalid data received" code means a control unit still receives messages from another module on the data bus, but the content of those messages is implausible, out of range or flagged as faulty.

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U0401 quick summary

Fault codeU0401
MeaningInvalid Data Received From ECM/PCM A
SystemNetwork / CAN Bus
VehiclesGeneric OBD2
SeverityMedium
Can I drive?Usually yes, but some functions may be disabled. If warning lights for brakes, steering or gearbox are on, have the car checked before driving further.
Repair cost€0 – €800

What "invalid data received" codes mean

Unlike "lost communication" codes, the bus connection works here: the messages arrive, but the values in them do not make sense – for example an engine speed of zero while the car is moving, or a signal that the sending module has marked as invalid because of its own fault.

In most cases the real fault is in the module named in the code or in one of its sensors. That module usually stores its own, more specific code, so the first step is to read it. Software versions that do not match, a module replaced without coding, and low voltage are other typical causes.

The receiving module may switch off functions that depend on the data – for example stability control, cruise control, start-stop or shift quality – until the data is valid again.

Symptoms of U0401

  • Several warning lights at once
  • Functions such as ESP, cruise control or start-stop not available
  • Gearbox shifting harshly
  • Code appears after a module replacement or software update
  • Code stored in several modules

Most common causes of U0401 (most likely first)

Mechanic's Pro Tip

Do not replace the module that stored the "invalid data" code – it is only the messenger. The problem is almost always in the module named in the code or in one of its sensors.

  1. 1.Fault in the sending module or one of its sensors

    Most likely

    Read the named module – it usually stores the root-cause code.

  2. 2.Module replaced without coding or with incompatible software

  3. 3.Low battery voltage or poor ground

  4. 4.Intermittent bus or wiring fault

  5. 5.Wrong vehicle configuration in the gateway

Step-by-step diagnostic guide

  1. 1

    Read all modules

    Read every control module and note the codes stored in the module named in the invalid data code.

  2. 2

    Fix the root-cause code first

    Diagnose and repair the specific fault in the sending module (sensor, actuator or internal fault).

  3. 3

    Check battery and grounds

    Check battery and charging voltage and the grounds of both modules.

    Multimeter: About 12.4–12.7 V at rest and 13.8–14.8 V with the engine running.

  4. 4

    Check coding and software

    Compare the module coding and software versions with the vehicle and look for updates or service bulletins.

  5. 5

    Clear and retest

    Clear all codes, drive the vehicle and rescan to confirm the code does not return.

Frequently asked questions

Can I keep driving with U0401?

Usually yes, but some functions may be disabled. If warning lights for brakes, steering or gearbox are on, have the car checked before driving further.

How much does it cost to fix U0401?

Typical repair costs are 0 € – 800 €, depending on the cause and the vehicle. The most common fixes are: fault in the sending module or one of its sensors; module replaced without coding or with incompatible software; low battery voltage or poor ground. Always confirm the cause with the tests above before buying parts.

What is the difference between "lost communication" and "invalid data"?

Lost communication means no messages arrive at all. Invalid data means messages arrive but their content is implausible or marked as faulty.

Can a software update fix these codes?

Sometimes, especially after a module replacement. Check for service bulletins and software updates for both modules.

What is the difference between U0401 and similar codes?

U0401 belongs to a group of codes for the same component that differ in the type or location of the fault: U0402 – Invalid Data Received From Transmission Control Module; U0403 – Invalid Data Received From Transfer Case Control Module; U0404 – Invalid Data Received From Gear Shift Control Module A; U0415 – Invalid Data Received From Anti-Lock Brake System (ABS) Control Module; U0416 – Invalid Data Received From Vehicle Dynamics Control Module; U0418 – Invalid Data Received From Brake System Control Module. The tests on this page apply to the whole group; the type of fault tells you where to start.

Related fault codes

This guide is for information only. Working on vehicles can be dangerous — if you are unsure, have the car checked by a qualified mechanic. Values can differ between model years; always check the manufacturer's repair information.