clio mk3 immobiliser problem

Hi to all



I have a problem with my

clio III - Dynamique s

1.4 Petrol

2006



Immobilizer light stays on and if I leave the ignition key on. The dash says low battery. But the battery is fully charged



So far I have changed the fusebox bsi ecu and ignition key coil but it still has the same problem.



Everything else works



I put key turn all lights on dash light up, I turn key once lights go out and nothing. The immobiliser light stays on and 2 minutes later says low battery



Really really confused and automotive electrician does not know what the problem is.



Thank you in advance for any help



kind regards Jess