What to do when a Loco does not Respond in DCC.

DCC is a 5 to 9,000 Hz square wave A.C. signal, that the microprocessor in the decoder has to decipher, to issue speed commands and function selection continuously for the decoder to operate. Sometimes the decoder does get confused for some reason. A reported common problem and it has happened to me. That when there is a short on the layout, the decoder acts “strangely” with some funny result. Sometimes the address CVs are affected which will prevent communication with the decoder. This is seen as a “locked up” decoder.

Sometimes this lock up could have been caused by “Operator Error”.

What should we do to correct this “lockup” or loco not operating situation? I have listed a few things below:

• Power: Move loco to a known clean track and check for power. This happens too often not to consider first.
• Consist Address One common operator fault is that we are trying to get a loco to move that was in a “Consist” previously. Program CV 19 to “0”. Also operating command station may not know Advanced consist address that consist was “set up” on another layout. Set CV 19 to “0” and rebuild consist if required.
• Command station may be 128 speed steps configuration and decoder only supports 14 speed step configuration. Reset C/S
• Manual Notching: If a diesel sound decoder, you may have this set. Set to auto notching.

If the loco still does not work after checking the above Place loco on the Program Track and read the following CVs.

• If “Cannot read CVs” or something similar shows on display, dirty wheels, faulty pickups or damaged decoder, rectify.
• CV 29 may be set incorrectly, ensure correct value for the required features especially which address is being used.
• CV 3 Acceleration set to high, reset to “0”

Note: Ensure acknowledgement of programming command by the small movement of the loco and/or a sound (sound locos).

If all else fails to get the loco to work do a reset.

• Reset the decoder on the Program Track. Most decoders are reset by writing 2 to CV 30. Refer to the Decoder Instructions and DCC system Manual. When a reset is done, the decoder will ONLY respond to the short address of “3”. You will have to reprogram the long 4 digit address if that was being used any CVs that you changed to fine tune motor and lights.

For both NCE TCS and Soundtraxx, to reset decoders, select CV 30, enter value of 2 and cycle power.

For NCE system users you can also do this at the Program Track and select option 7 “Recovery Programming” with the new eprom.

See also Resetting Decoders at the Model Railroad Craftsman.

Programming difficulties for a new Sound Loco on the Program Track.

Some DCC systems cannot program sound locos especially BLIs. Confirm running of loco on default short address if possible and then Program on the Main. Some modelers are using the Power Pax from DCC Specialties to give more power on the Program Track.

Sometimes the loco comes from the factory using last two digits of road number, depending on model. Check included instructions for what number to address loco with. Remember without the “correct address” nothing happens.

BLIs and others that have QSI sound boards with DC running capability, may have a switch that has to repositioned for DCC.

If a BLI does not run on an Atlas or Roco DCC system then track voltage may be too high > 22 volts DCC.

Programming

If loco does not program, then motor or motor connections may be faulty.

If you cannot program on Program Track attempt to Program on the Main, maybe faulty program track wiring or faulty switch. This may result in difficulty or weird funny results.