Runaway locomotives

[C37]

I have bought second hand a Bachmann Blue Midland Pullman set.
The previous owner operated DC and had put blanking chips in place of the fitted DCC chips.
I've put the original 21 pin DCC chips back into each power car.
As soon as I set either car on the DCC track to programme, they set off, at full speed. This is happening to both power cars.
I use an NCE Power Cab.
Any ideas what is happening and how I can programme the locos to work on my DCC layout?
Thanks

[brian1951]

You need to set the decoder so it does not run on DC

[C37]

Thanks, as soon as I put the loco on the track the wheels set off at full speed! Is there any way of setting the decoder without the loco running off, am I going to have to use a rolling road or something?

[brian1951]

Try a new piece of track to program on, make sure its clean.

[C37]

Same result, as soon as I put it on the track it races off at full speed

[brian1951]

Have you just got two wires from the power cab to the track. Are you sure the loco has a decoder fitted ?

[C37]

Yes, I removed the blanking plates, fitted the decoders which, put it on the track and they just race off

[brian1951]

Is your programing track totally separate from your main track ?

[RAF96]

Can you force the Power Cab into Programming Mode before you put the loco on track.

[C37]

Yes, programming track is a single length of peco code 100 flexi track.

How do I force programming mode?