Securitech 800L , how to change engineering code?

[Mike]

Hi,
Our new house had the above system fitted when it was built about 3
years ago.
Recently I fitted a PIR in to the garage on Zone 7 which was spare.
(it had
a short accross the C/NC connectors)

However for some reason the red led on this zone seems to come on, I
think when
the zone is triggered.
I'm wondering if this zone is programmed in some other way?

I need the engineering code to check this, however it is not the
default 7890 which is shown in the installers manual. Anybody know how
to change this, or if its even poissible?

Thanks
Mike