Oven showing f4 even after replacement of temp...

chain of events. oven stopped working, I had repair company come out and they said I needed a new control board (they didn't check anything else). I looked online and saw the posting about reseting the breaker and tried that instead. Once I reset the breaker inside the oven, then the f4 showed and oven did not work. Repair company came out and said it needed temp sensor. They replaced the temp sensor but oven still does not work and f4 still displays when I try to turn it on. The repair company wants to come out again with an "oven table" to take the oven(s) out of the built in cabinet and look behind it for loose wires,etc. I've already spent $200 having them out multiple times and for the new temp sensor. Should I have them look at it again? Any ideas of what I could check on my own before I spend more money for them to just look for a problem?