My '98 F150 5.4 triton the airbag light flashes 5 then 2 for 5 series then stays on. I checked the fuse and it isn't tripped. Don't know where to go next any advice.

 

A code 52 tells you that the backup power to the module is in a fault condition.
What this means is even in an accident that cuts power to the truck by smashing the battery or cutting a cable etc. The module is supposed to still fire the bags from voltage stored in this capacitor.
Look for the fuses that supplies the RCM module device and test it with a meter. If good then the fault is at another point but be careful working on the system and around the sensors with battery power applied.