first things first.....
are you sure about that model number?
I don't know about the MCFE database but the MCFA database doesn't show a FD25T model, it only shows FD25, FD25K, FD25N and FD25NT. I checked in the FD25NT model and there was not much on any error codes.

secondly....
got a serial number? that might help just a bit

thirdly....
gas/lpg truck? or S4S diesel? (well assume LPG)

fourthly....
that code if it is indeed an "E-34" then yes it is an ignition fault code
BUT... if it is an "F-34" then it is a speed sensor code

These systems are capable of producing many different types of codes starting with different prefix letters such as E, F, D, P, L and S so just stating it has "error 34" is too generic and more detail is needed if you want a more accurate diagnosis and not just a bunch of guys guessing at it.

Accuracy of information makes all the difference in the world ;o)