Programming Track Setup Issues

Hello,

I've been trying to get back into the model railroad hobby after a long hiatus, and am discovering a lot of cool features that I'd like to use. I had a Digitrax DCS 50 as a kid and had no idea that it could program the decoders and am trying to set up a programming track. However, I keep getting a D nD error whenever I try and read or write a decoder address. I've tried with two different locomotives (One Athearn, no sound, and one Broadway Limited Imports, with sound) and both give the same error. A digitrax website said to put a resistor in the Prog A and Prog B outputs, and when I tried that, the Broadway limiteds sound and lights cut on when I attempted to write the decoder address. I'm sure that I've got my wires hooked up right. I read a constant ~1.5 volts on the programming track.

What am I doing wrong?

Thanks in advance!