U0401 Invalid data received from engine control module (ECM/PCM A)
What U0401 means
Modules in a car share data over a network (CAN bus). U0401 is stored by another module, often the transmission, ABS or instrument cluster, when the messages it receives from the engine control module are present but implausible or out of range. The root cause is usually a fault inside the engine computer, its power supply or the network wiring.
U0401 is a generic SAE J2012 code: it means the same on every make. The exact cause still depends on the car, so read the freeze-frame data before replacing parts.
At a glance
- Severity
- Medium
- Typical repair cost
- 80–1500 €
- Workshop time
- 1–5 h
- Repair difficulty
- Hard
- DIY possible
- No
- Check engine light
- Yes
- Affects emissions test
- Yes
- Limp mode possible
- Yes
Parts and labour at an independent workshop in Europe. Main dealers charge more; the cause decides the bill, not the code.
Symptoms
- Several warning lights on at once
- Transmission or stability control in a reduced or limp mode
- Gauges reading incorrectly or dropping out
- Other engine codes stored alongside
Common causes
- Fault already stored in the engine control module that makes its data invalid
- Low battery voltage or poor ground at the engine control module
- Damaged or corroded CAN bus wiring or connectors
- Engine control module software that does not match other modules after a repair
- Failed engine control module
Can I keep driving with U0401?
You can usually drive carefully, but have it diagnosed within one or two weeks. If the transmission or stability control goes into limp mode, drive only as far as a workshop.
What to check first
- Read codes from all modules, not only the engine; fix any engine fault codes first
- Check battery voltage, charging voltage and the main grounds of the engine control module
- Inspect CAN bus connectors near the engine computer for corrosion or water
- Check for software updates for the engine control module before replacing any module
Related codes
- U0412 Invalid data received from battery energy control module A
- U0415 Invalid data received from ABS control module
- U0422 Invalid data received from body control module
- U0428 Invalid data received from steering angle sensor module
- U0433 Invalid data received from front distance range sensor
- U0252 Lost communication with rear lighting control module B
- U0184 Lost communication with radio
- U0140 Lost communication with body control module
Data: TORKO fault-code catalogue, built on OBDex (CC0-1.0) and reviewed against workshop practice. Informational only — it does not replace a diagnosis by a mechanic.
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