I first researched the LG model on web on how to check for F9 code problems. Was told to use electronic meter to check terminals on heat sensor, bake and broil elements first. If they were ok then check the oven pcb assembly. Found no reading on the pcb so I ordered a new pcb board. That took care of the problem. Spent about $55.00 for replacement part Much better than having a technician come check the unit.