U0401 means Invalid Data Received From ECM/PCM A. A module received a message from the ecm/pcm a but the data was out of range or did not make sense. It is a generic OBD-II code, so the definition is the same on any make, but the most likely cause varies by engine; confirm with a scan tool and the service information for your vehicle before buying parts.
What U0401 means
Modern vehicles have many control modules that share information over a network, usually called the CAN bus. Codes starting with U mean a module has stopped hearing another one, and voltage and processor codes mean a module is not getting clean power or has an internal fault. Low battery voltage, poor grounds, blown fuses and damaged wiring cause many of these codes, so test the battery and charging system first.
U0401 symptoms
- Warning lights
- Features working erratically
- Check engine light on some vehicles
Common causes of U0401
- Fault in the sending module or one of its sensors
- Software mismatch after a module replacement
- Low voltage or poor grounds
- Network wiring problems
How to diagnose U0401
- Read codes from the sending module
- Check module software versions
- Check battery voltage and grounds
- Inspect network wiring
Can you drive with U0401?
It depends on the system affected; get it diagnosed.
U0401 tips
Invalid data codes often point to a fault inside the sending module, such as a failed sensor input; read the engine computer’s own codes first.
Will U0401 clear itself?
If the fault stops, the computer turns off the check engine light by itself after several drive cycles without seeing it again, and the code stays in memory as history for a while. Clearing U0401 with a scan tool after a repair is fine, but if the cause is still there the code returns, sometimes within one drive. Disconnecting the battery also clears codes on most vehicles, but it erases learned fuel trims and idle settings as well.
Related codes
| Code | Meaning |
|---|---|
| U0100 | Lost Communication With ECM/PCM A |
| U0101 | Lost Communication With TCM |
| U0140 | Lost Communication With Body Control Module |
Guides that help
When it is more than a sensor
Voltage and network codes come from wiring, the battery, the charging system or a module, not from engine or transmission wear. If a lost-communication code has left the transmission in limp mode, rule out the module and wiring before deciding the unit has failed, and see our transmissions only if testing confirms internal damage.
Shipping is a flat $80.00 per order to US addresses, with 15-day free returns. Questions? Ask a parts specialist.