Faulty or failing control module that is transmitting corrupted or out-of-range data onto the CAN bus; Software or firmware defect in one of the modules, often resolved by a manufacturer update; Poor electrical connection at a module connector, causing voltage drops that distort message content; CAN bus wiring damage or chafing that introduces interference without fully breaking communication; Low battery voltage or a failing charging system that causes modules to transmit invalid data during voltage sags; Aftermarket electronic devices wired into the CAN bus that inject non-compliant messages; Internal failure of the receiving module's CAN transceiver, causing it to misinterpret valid data as invalid

DTC codes / U04xx · Invalid data received from a module / U0400

U0400Invalid Data Received

Q: What does code U0400 mean?

Invalid Data Received. U0400 is a communication fault where a control module receives data from another module over the vehicle's Controller Area Network (CAN) bus but determines that the data is invalid or corrupted. The receiving module sets this code when the message content fails its internal plausibility or checksum validation, even though the physical network connection is intact.

U0400 is a communication fault where a control module receives data from another module over the vehicle's Controller Area Network (CAN) bus but determines that the data is invalid or corrupted. The receiving module sets this code when the message content fails its internal plausibility or checksum validation, even though the physical network connection is intact.

SystemNetwork

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyProfessional

AreaInvalid data received from a module

Symptoms you may notice

Illumination of the malfunction indicator lamp (MIL) or a message on the driver information center
Often no symptoms besides the warning light, with the vehicle driving normally
Intermittent operation of systems controlled by the affected module, such as lighting, climate control, or driver aids
Multiple unrelated warning lights appearing simultaneously if the invalid data affects several modules
Rough running or transmission shift quality changes if the corrupted data involves powertrain messages
A stored U0400 code with no other communication codes present, indicating a data content issue rather than a bus wiring fault

Common causes, most likely first

Faulty or failing control module that is transmitting corrupted or out-of-range data onto the CAN bus
Software or firmware defect in one of the modules, often resolved by a manufacturer update
Poor electrical connection at a module connector, causing voltage drops that distort message content
CAN bus wiring damage or chafing that introduces interference without fully breaking communication
Low battery voltage or a failing charging system that causes modules to transmit invalid data during voltage sags
Aftermarket electronic devices wired into the CAN bus that inject non-compliant messages
Internal failure of the receiving module's CAN transceiver, causing it to misinterpret valid data as invalid

How to diagnose and fix it

Connect a scan tool and record all stored codes, freeze-frame data, and module identification to determine which module set U0400 and which module is sending the invalid data
Perform a battery and charging system test to rule out low voltage as the root cause of corrupted messages
Inspect and clean the connectors at both the receiving module and the suspected transmitting module, looking for corrosion, loose pins, or water intrusion
Check the CAN bus wiring for chafing, pinched sections, or poor grounds that could introduce interference
Verify that all modules have the latest manufacturer software updates, as invalid data codes are frequently resolved by a reflash
If a specific transmitting module is identified, substitute a known-good module or perform a module swap test to confirm the fault follows the module
Clear codes and road test the vehicle under the conditions recorded in freeze-frame data to confirm the repair

Why U0400 is rarely a wiring fault

U0400 is often misdiagnosed as a CAN bus wiring problem, but the code specifically means the data content is invalid, not that the bus is physically disconnected or shorted.
A weak or failing battery is a common hidden cause because modules may transmit corrupted messages during cranking voltage drops, setting U0400 without any hard fault.
Aftermarket accessories such as dash cameras, alarm systems, or piggyback tuners tapped into the CAN bus can inject invalid messages and trigger this code.
The code does not always indicate a failed module; a software bug in a single module can broadcast invalid data that affects multiple receivers, and a reflash often resolves it.
U0400 can be stored alongside U0100 or U0140 when the invalid data originates from a module that also has intermittent power or ground issues.

Can I keep driving with U0400?

The vehicle is generally safe to drive if it runs and shifts normally, but avoid long trips or towing until the fault is diagnosed because the invalid data could affect safety-related systems without warning. If multiple warning lights are present or the vehicle enters limp mode, stop driving and have it inspected promptly.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.