U0406 indicates that the powertrain control module (PCM) has detected invalid or implausible data being received from the fuel injector control module (FICM). This communication fault suggests a problem with the FICM itself, its wiring, or the data bus linking the two modules.
The FICM may have an internal electronic fault causing it to send corrupted or no data to the PCM.
Open circuits, short circuits, or corroded terminals in the communication or power lines can disrupt data transfer.
A fault on the controller area network (CAN) bus, such as a short to voltage or ground, can corrupt messages from the FICM.
Insufficient voltage or a poor ground connection can cause the FICM to operate erratically or cease communication.
Although uncommon, a PCM internal fault could misinterpret valid data from the FICM; this should only be considered after all other causes are ruled out.
No. PCM failure is a rare cause of U0406; the fault is almost always in the FICM, its wiring, or the communication bus. Replacing the PCM without thorough diagnosis will not fix the code.
Yes, low system voltage can cause the FICM to send invalid data; always verify battery and charging system health first.
The vehicle may enter limp mode or stall; driving is not recommended until the cause is repaired.
Improper calibration or software mismatches between the PCM and FICM can trigger this code; revert to stock programming to test.