newbee- engine emissions light came on? how bad could it be??

[bongo]

hi everyone,
new to the forum.
i bought my 2001 4.4lt x5 lpg, 5 days ago, after having the usual problems with my 1998 range rover.
on the 2nd day of owning it the engine light came on.
in the owner manual it says "deterioration of exhaust emission control values"
it seems to run fine, and its going on the diagnostics tomorrow.
but could someone tell me what the worst case scenario would be with this please.
thanks

p.s. i've got to say i absolutley love the car!