Did you try the other PS2 engine in conventional mode?
I did... Neither worked in conventional or DCS...
Sounds like something happened to the locomotives, not the DCS system. When you tested conventional, the DCS system was totally out of the picture and turned off?
Is there nay chance that these engines have a 2-Rail/3-Rail switch that's not in the 3-Rail position?
I'm sure no expert, but if the locomotives don't work in either conventional or DCS, that pretty much narrows the problem down to the locomotives, not the control system.
The first thing I would do is check underneath both engines to see if, as Barry noted, there is a slide switch that has been set in the wrong position (the owner's manual should show where it is). That is especially true if the engines were other than new-in-box when purchased.
Allan's right, I can't see how this is the DCS system.
