U0400
Invalid Data Received
Network / communication
Generic OBD-II
Medium
What it means
U0400 is a generic network code meaning a module received data over the communication bus that was out of range or implausible, without naming a specific source module. What it means for you depends entirely on which signal went bad — anything from a single disabled feature to powertrain limp mode — so the first step is scanning for the companion codes that point to the real culprit.
Medium
Can I keep driving? Depends on the source — a module is reporting implausible data over the bus; effects range from a disabled feature to limp mode, so scan for companion codes first.
Common symptoms
What you'll notice
- Check-engine or module warning light on
- Feature or system tied to the bad data not working correctly
- Reduced-power/limp mode if the invalid data affects the powertrain
- Companion 'invalid data' or 'lost communication' codes stored in other modules
Common causes
Most likely first
- A module transmitting out-of-range or implausible values onto the CAN busLikely
- Sensor feeding a module corrupted or impossible readingsCommon
- Wiring, connector, or ground fault corrupting bus dataCommon
- Software or configuration mismatch after a repair or module swapLess often
How to diagnose & fix
Work through it in order
- Scan every module and read all stored codes, including the companion codes, to find the source.
- Check freeze-frame data to see which signal was flagged invalid.
- Inspect the wiring, connectors, and grounds for the implicated module.
- Test the sending module and its sensor; reprogram or replace as needed, then clear and re-test.
FAQ
Quick answers
Is it safe to drive with U0400?+
It depends on which module is sending bad data. If the powertrain is affected you may get limp mode; if it's a comfort feature, driving is fine. Scan for companion codes to know which.
Can I just clear U0400?+
It returns until the source of the invalid data is fixed. Use the companion codes to identify and repair the actual sending module.
Related codes
Often seen with U0400
Read & clear U0400 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX