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U0401: Invalid data received from the engine control module (ECM/PCM)

Another module is receiving impossible or inconsistent data from the engine ECU. Usually a faulty engine sensor or a software mismatch is behind it.

Code U0401 at a glance
CodeU0401
SystemCommunication network
GroupU04xx, Invalid data between control units
TypeGeneric: it means the same on every make
Can you keep driving?With care

What U0401 means

The engine ECU (ECM or PCM) shares data such as revs, load, temperature and throttle position over the network. This code is stored by another module, for example the gearbox or ABS unit, when messages arrive but with out-of-range values or errors. The engine ECU often has its own codes that explain the source.

Most common causes

  • A faulty engine sensor whose reading is passed on (check the P codes stored at the same time)
  • Low or unstable battery voltage
  • Loose or corroded engine ECU connector
  • Interference or damaged network wiring
  • Engine ECU with the wrong software, for example after replacement or reprogramming
  • Faulty engine ECU

Symptoms

  • Engine or other warning lights on
  • Harsh shifts or gearbox in limp mode
  • Stability control or cruise control disabled
  • Strange readings on the dashboard gauges

Can you drive with U0401?

With care You can drive with care, but the car may go into limp mode or lose some aids. Have it checked soon.

How to check it

Read codes from every module, not just this one: engine P codes usually point to the sensor at fault. If the ECU has recently been replaced or reprogrammed, tell the garage.

How to read and clear U0401 with Final OBD

Plug an OBD2 scanner in under the steering wheel, switch the ignition on and open Final OBD. Under Faults you’ll see U0401 with this same explanation and whether it’s confirmed, pending or permanent.

With Free you read this code with its short description for nothing, and clear it if the engine stores it over standard OBD. With Pro you get the full explanation, how the car was running when it was logged (revs, temperature, load) and clearing in every control unit.

Clearing the code only turns the light off: if the cause is still there, it comes back. Clear it once it’s fixed, and not right before the ITV. It’s all in how to read and clear fault codes and in the ITV and OBD.

Similar codes

U0401 is a generic code, so it means the same on any make, for example on Alfa Romeo, Dacia, Jeep, Kia, Nissan, Škoda. See what Final OBD does on your car in makes and models.

What does code U0401 mean?

The engine ECU (ECM or PCM) shares data such as revs, load, temperature and throttle position over the network. This code is stored by another module, for example the gearbox or ABS unit, when messages arrive but with out-of-range values or errors. The engine ECU often has its own codes that explain the source.

Can you drive with U0401?

You can drive with care, but the car may go into limp mode or lose some aids. Have it checked soon.

How do you clear U0401?

With an OBD2 scanner and an app like Final OBD, which clears it for free if it’s stored by the engine control unit. But clearing it only turns the light off: if the cause isn’t fixed, U0401 comes back.