2008 Hyundai i30. 2.0 litre petrol. (Elantra selected, since I believe i30 is same basic engine system as the Elantra, and i30 is not a provided option for my model on this forum). Car won't start. Engine immobiliser warning light illuminated. Spare key wont work either. The engine turns over fine (not a flat battery). Do I need to reset the engine immobiliser? Can I disable the engine immobiliser?

Interesting problem.. since not US spec. Is there a 'remote keyless (fob)' programmed for this vehicle? That's the only way to DE-arm the immobilizer (anti-theft) feature (based on US specs). Unless you have this key fob (keyless entry remote... which must also be programmed for this vehicle), the only other way is wait 5 minutes with the existing key in the ignition, then it should start (US specs). You will still need to have an 'ACTIVE' keyless remote programmed for this vehicle... otherwise, you'll continue to run into this problem.