The command station in this case, the DB150 does not support CV read back. The DT402D can read and display CV's just so long as the command station supports that feature. The DB150 does not, so you will not be able to read CV's this way. (BTW, this is one of the main differentiating features between the DB150 and the Super Chief command station the DCS100)
If you want to read back CV's with the setup you have you will need to setup a stand along program track with the PR3. (This is well documented in the manual) and then use the PR3 connected to Decoder Pro on a PC.
You have had the PR3 for some time, how have you been using it? Are you using it as the PC interface to the Loconet? Remember, the PR3 can be used in 2 ways, first as a direct connection PC interface between the loconet and your computer. You won't be able to read CV's this way, because of the DB150, or as a stand alone program environment, you will be able to read CV's this way.
Simon Modelling CB&Q and Wabash See my slowly evolving layout on my picturetrail site http://www.picturetrail.com/simontrains and our videos at http://www.youtube.com/user/MrCrispybake?feature=mhum
I am trying to read back the CV installed in my HO scale International Hobby Corporation GG1 locomotive. I have a Digitrax DB150. I followed the instructions on the DT402 manual and when I press the display key it reads Ad4= = rd followed by a blinking square and then a fail message instead of Ad4=8rd followed by a flashing box. I guess it can not read back the CV because I am using a DB150. I also have a Digitrax PR3 and Java Model Railroad Interface software. I guess I can solve this problem by getting the plug in Loconet device that was mentioned earlier. What is that Loconet device and where can I purchase it from. Or can I just use JMRI Decoder Pro.