There are certain numbers that the Pektron won't accept because they are "reserved" by MG Rover. If pscan won't let you choose one like 1111 then that will be why.
Thanks. Yes, I noticed this whilst changing the EKA code at the weekend. 1111 is not accepted. But I managed to find suitable low numbers which were accepted and served my purpose. Pscan is quite easy in this respect in that it is impossible to enter an unacceptable code.
Once everything is sorted, I will probably change it back to the original code. Whilst this is cumbersome to use, it will match the original data.
Whilst I try to resolve my original problem, I have temporarily replaced the horn with a little 12v buzzer. This saves me from annoying my neighbours