According to Sountraxx the decoder installed in the Spectrum units is a reduced function set and Fireman Fred is one of the functions not available.  So for those of you that are trying to get this function to work, you can stop trying it is not there.

Did Bachmann include the Fireman Fred features in the sound decoder they are installing in their Spectrum 2-8-0s?  I just purchased one and have everything working except Fred and that is with shovel volume set to 255 and shovel probability set to 255.