The EC is an indicator, not usually a fault in itself. You need to put an A/C person on this. The refrigerant only gets out if there is a leak, so you need to find and fix that. Unfortunately if the computer is seeing a sensor fault that keeps it from engaging the A/C you will need to get SDS on there and read out the codes. A good A/C person might be able to suss it out with just gauges and experience, if you don't have SDS available.