running TMCC And DCS engines with DCS handheld

Sounds like poor signal strength from the command base. Not sure what you refer to in a ground wire from Legacy base to TIU.  Nothing I'm familiar with.  Sounds like a connection that could kill the TMCC signal by messing with the ground.   The ground is critical to TMCC transmission.

The TMCC/Legacy bases are grounded through the wall-wart power supply and it works best plugged into a wall outlet with a good earth ground (e.g., up to current code).  Sometimes the ground does not function well if the command base power supply is plugged into a house outlet that has a poor earth ground (as in much older homes) or is plugged into a power strip/surge protector that interferes with the ground connection.  Hope this is the solution, as it is an easy one.

To make sure the TMCC command base is functioning, you could try using it independent of the DCS system.  This assumes you have a cab-1.  Just connect the command base to the outside rail and see if that works.  Assuming the command base power supply is properly grounded as above.

After you hit the D for done when you entered the engines name. Did you assign it’s TMCC I.D. into the remote ? That would be the number you use to address it with your TMCC or Legacy remote.  After this you have to let the system know the I.D. number of the TIU that you have the Legacy cable plugged into. If you are not sure of the number. Count the number of blinks when you power it up.

@Bert39 posted:

I have successfully "ID" the TMCC engines in TMCC system and they run correctly. I then enter them into my DCS handheld as instructed and they appear on the screen as they should I select  a TMCC engine but nothing happens they will not run. The Legacy unit registers the signal to the engine. I have the MTH cable to connect the Legacy unit to the TIU have run the ground wire to the TIU from the Legacy base, I have done this with several TMCC engines with no success, what is wrong!

Bert,

Where do you have the Legacy base common wire (a.k.a. “U”) wired to? Pictures help a lot when debugging setups such as yours.

Also, which cable do you have to connect the TIU to the Legacy base?

I have the other end of the Legacy "U" terminal connected to the TIU black Fixed term which goes to the common rail (outside).

@Bert39 posted:

I have the other end of the Legacy "U" terminal connected to the TIU black Fixed term which goes to the common rail (outside).

Connected to TIU input or output?

Suggest that you check the cable, Are you using MTH 50-1032 TIU to Legacy base cable?