If the decoder is otherwise working properly (i.e., responds properly on the mainline to speed and direction commands), but the command station is having trouble reading CV data from the decoder, it may be due to incompatibilities between the electrical requirements of the sound decoder (which are different from conventional decoders due to the added audio circuitry) and the electrical characteristics of the programming track.
In this case, you will need to use a programming track booster, such as the PTB-100. The PTB-100 amplifies the programming track signals to levels that work best with SoundTraxx Sound Decoders. It is easy to install and inexpensive. An advantage to using the PTB-100 is that it also provides short circuit detection and some helpful diagnostics.
The PTB-100 is neither needed nor recommended for use with the Zimo MX1 or the Lenz LVZ100.