Corroded, loose, or damaged wiring and connectors at the fuel injector control module or its CAN bus splice points; Failed or failing fuel injector control module, often due to internal circuit faults or heat damage; Low battery voltage or poor charging system performance causing the module to send corrupted data; CAN bus wiring faults such as opens, shorts to ground, or shorts to voltage on the data lines; Software or calibration mismatch in the fuel injector control module after a replacement or reflash; Water intrusion or contamination in the module connector or harness, leading to intermittent invalid signals; A separate module on the same bus flooding the network with errors and disrupting injector control messages

DTC codes / U04xx · Invalid data received from a module / U0406

U0406Invalid Data Received From Fuel Injector Control Module

Q: What does code U0406 mean?

Invalid Data Received From Fuel Injector Control Module. U0406 is a communication fault where the engine control module (ECM) or another controller on the controller area network (CAN) bus receives data from the fuel injector control module that it considers invalid or out of range. The computer has detected that the module is responding but the content of its messages does not match expected values, so the ECM cannot trust the injector control data.

U0406 is a communication fault where the engine control module (ECM) or another controller on the controller area network (CAN) bus receives data from the fuel injector control module that it considers invalid or out of range. The computer has detected that the module is responding but the content of its messages does not match expected values, so the ECM cannot trust the injector control data.

SystemNetwork

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyProfessional

AreaInvalid data received from a module

Symptoms you may notice

Illuminated check engine light or service engine soon light, often with no other noticeable symptoms
Rough idle, misfire, or hesitation under acceleration if the invalid data affects injector pulse width
Reduced engine power or limp mode triggered by the ECM when injector control data is deemed unreliable
Intermittent stalling or hard starting, especially when the fuel injector control module signal drops out
Poor fuel economy or rich/lean running conditions reported by the driver
Other communication-related warning lights if multiple modules share the same CAN bus segment

Common causes, most likely first

Corroded, loose, or damaged wiring and connectors at the fuel injector control module or its CAN bus splice points
Failed or failing fuel injector control module, often due to internal circuit faults or heat damage
Low battery voltage or poor charging system performance causing the module to send corrupted data
CAN bus wiring faults such as opens, shorts to ground, or shorts to voltage on the data lines
Software or calibration mismatch in the fuel injector control module after a replacement or reflash
Water intrusion or contamination in the module connector or harness, leading to intermittent invalid signals
A separate module on the same bus flooding the network with errors and disrupting injector control messages

How to diagnose and fix it

Perform a full scan of all modules and record all stored codes, then clear codes and test-drive to see if U0406 returns immediately or intermittently
Inspect the fuel injector control module connectors and harness for corrosion, loose pins, chafing, or water intrusion, and repair as needed
Check battery voltage and charging system output under load to rule out low voltage as the cause of corrupted module data
Measure CAN bus resistance and voltage at the diagnostic link connector to verify bus integrity and rule out wiring faults
If wiring and power are good, substitute a known-good fuel injector control module or perform a module reflash/calibration per manufacturer procedure
After repair, clear codes and verify that U0406 does not reset during a road test that includes idle, acceleration, and steady cruise

What the invalid data really means

U0406 does not mean the fuel injector control module is dead; it means the module is alive enough to communicate but its data content is out of range, so a no-start condition is less common than with a no-communication code.
A weak or failing battery is a frequent hidden cause because low voltage can corrupt the module's internal calculations without setting a low-voltage code first.
Technicians often replace the fuel injector control module only to find a corroded ground or a chafed CAN wire at a splice pack was the real problem, so always inspect the harness before condemning the module.
This code can be set by a module that has been incorrectly programmed or has mismatched software after a replacement, so verify calibration before assuming a hardware failure.
Other modules on the same CAN bus can cause U0406 indirectly by flooding the network with invalid frames, so a full network scan is essential before focusing only on the injector control module.

Can I keep driving with U0406?

The vehicle may be safe to drive short distances if it runs normally and only the warning light is on, but avoid heavy acceleration, towing, or long trips until the fault is diagnosed. If the engine runs rough, misfires, or enters limp mode, stop driving and have the vehicle 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.