An F1 code indicates a problem with the touch pad or membrane. Replace the touch pad or membrane. F1 can also indicate an issue with the oven's on-board watchdog system, which requires replacing the touch pad or clock assembly.
An F2 indicates your oven is getting too hot. In this case, replace either the relay board (if your model has one) or the heat sensor.
F3 or F4 Codes
F3 and F4 indicate a problem with your oven's heat sensor. This problem is similar to an F2 issue, but these codes indicate a heat sensor only as opposed to the relay board.
F5 indicates watchdog and hardware circuit disagreement. Replace the clock assembly.
F6 indicates a missing AC signal, which is caused by improper voltage in the unit. Repair it immediately.
F7 and F0 Codes
F7 indicates your oven has a shorted button or a button that has become stuck. A shorted button will probably need professional repairs. You can fix a stuck button on your own. F0 is a stuck function key.
F8 indicates the clock assembly needs replacing. The trouble is with the analog or digital circuitry.
An F9 code indicates trouble with the door latch, typically repaired by replacing the latch.