The first thing to do is to trip BOTH of the TWO circuit breakers that go to 220 VAC appliances like electric ranges and electric clothes dryers, pull the stove out and remove the back panel. It may just be something dumb like a burnt off wire. Maybe somebody at the factory didn't crimp a terminal onto the wire properly, and it's burnt off. Or, maybe they just didn't push the terminal onto a tab with anything resembling conviction, and it just fell off. The appliance manufacturer would not crimp a terminal onto a wire and just have it dangling free and unconnected in the range. So, any terminal hanging loose is your prime suspect if you don't see a wire with it's end burnt.
If that doesn't lead to anything, the first thing I'd do is contact your local Frigidaire factory authorized service depot and ask them what the oven thermistor resistance should be at room temperature. If I recall correctly on the 21 Frigidaire ranges I bought about 10 years ago, the thermistor at room temperature should read about 1000 ohms. Check the thermistor resistance because it's the eye's and ears of the oven control.
That thermistor replaces the old oil filled bulb that used to be connected via a capillary to the oven thermostat. It tells the oven's electronic control what temperature the oven is because it's resistance changes as the temperature changes. If your thermistor has gone south, then the oven control doesn't know what's happening in the oven.
If you can't see anything wrong in the wiring at the back of the oven, and the oven thermistor is working OK, then I think you really need the assistance of an appliance repair tech.
Both of these sites are owned and operated by appliance repair techs, both have Q&A forums on them, and in both cases the owners of the sites donate their spare time answering appliance repair questions on their web sites:
Appliance411 - Appliance Purchasing, Appliance Service and Appliance Repair Parts Information Center for Major Home Appliances
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When I first got on the internet, I tried answering some of the appliance repair questions on Dan O'Neill's web site, as I thought I'd be doing him a favour. It was a total embarrasment cuz he's a professional appliance repair tech and I'm not. Him and the other appliance repair techs just blew my doors off, but they were polite enough not to say anything about it to me. However, in this case, if no one on this forum really knows what the problem is, it makes sense to advise you to seek out more knowledgeable advice.