Help, Check engine warning

The check engine warning does not go out on my 2.5D P38. The tale started after the central locking stopped working for a short time.
Car has been in LR dealer, they have cleared a number of faults down, and said all was well. All warnings out.
However the light is remaining on. The car drives ok, changes up stc, maybe holding gears longer than before.
Anybody got any clues?

Update, re-fitted Tigapglets hot starting mod this morning. Now the check engine light is out. Also the map seems to have reverted to the original fueling and speed mapping. The car runs normal, but with good hot starting.
Wonderful cars these they seem to adapt to change and self learn, and heal ... hahaha.