Safe to driveUntil the next service
J1939 code SPN 1408. Below — how the fault is worded at the factory by Ford Trucks, and what the second half of the code (FMI) means in the standard.
Ford Trucks/Ecotorq writes fault numbers in its own format: the code in the table below is a Ford code (hexadecimal, zero-padded), not a J1939 SPN. It matches the standard only where the signal itself is standard, and usually matches the title of this page by digit alone.
| FMI 12 | Wheel Unit Battery Low WU3A |
| SPN 1408 FMI 121408/12 · 1408.12 | faulty device or component |
Safe to drive. Below — how much time you have and what happens if you keep going.
A standalone fault with no immediate consequences for driving.
Show the codes at the next service. If a second code from the same system appears, stop putting it off.
Scanner threw several codes at once? Paste the whole list — we will show which one is the root cause and which ones simply followed.