2001 Renault Clio immobiliser

hi, ive have a 2001 clio dci i bought in january 5 hour drive away, got home fine and ran great for a few more weeks then one day it wont start / battery so i had it jump started and went of and bought a new battery they checked the alternator and its fine old battery came up faulty/ replace, great went on my way, a few weeks later went to the car dead, not a sound only a click from the glove box, and a flashing red light, so after a bit of investigation i press the button on the key while turning the red light goes solid then of and it will start and went on like this till the other day when my mechanic mate decided to sort it all out, checked all the wires and relays and they had oxidized , cleand em same with relays and fuses in the engine still the same so then he opened the ecu plugs put it all back now i have no glow plug light showing and the car wnot start at all, he thinks its not getting a live feed to the ecu from somewhere, im at a loss i need help please, anyone got any ideas would be very gratefull, thankyou