Dealing With Your SPN 3515 FMI 10 Fault Code

Seeing the spn 3515 fmi 10 flash on your dashboard is enough to make any driver let out a heavy sigh, especially when you're mid-haul and just want to get to your destination. It's one of those modern diesel engine headaches that reminds us just how complex our trucks have become. Basically, your truck's computer is telling you that the Diesel Exhaust Fluid (DEF) tank temperature sensor is acting a bit erratic. It's not necessarily saying the sensor is "dead," but rather that the information it's sending back doesn't make any logical sense to the Engine Control Module (ECM). ...

May 17, 2026 · 7 min · Alcantar Warman