Renault modules 1500 diesel engine car won't start?

Car won' t start was told it was the fuel injector but the mobile mechanic diognoise a air pocket in the fuel tank after plugged into his system.also the fob activate the door wasn't working. After testing and raving the engine with something attach to the battery everything seemed OK .Can down today and fob don't work the car is completely dead only had car for 6 weeks 12 year old car 12 month warranty car dealer stop trading need a car because mobility problems.