The controller assy is most likely bad.

$104.49 at sears for MC Part number: PKCPSWKT00
http://www.searspartsdirect.com/partsdirect/part-number/PKCPSWKT00/0022/815?pathTaken=partSearch&filterPart=&pop=flush&prst=0&shdPart=PKCPSWKT00


However here is an OEM controller part for $53.00
http://www.repairclinic.com/Shop-For-Parts?s=t-PKCPSWKT00-%3d%3d

(Manufacturer part number PKCPSWKT00 is RepairClinic item number 1488615.)
http://www.repairclinic.com/PartDetail/Control-panel-complete/1488615

Unless there is a broken wire or very bad terminal connection inside the microwave the controller is the most probable failure.

Thanks for choosing FixYa,
Kelly

Hi,

Here is a tip that will help you to figure out what is wrong with your Microwave Oven....

Basic Microwave Oven Troubleshooting Tips

heatman101