William J Hilton Head Island , SC September 01, 2016 Appliance: Maytag 30" Built-In Double Electric Oven Convection JJW8630DDS30 Jenn aire double wall oven turned off after a minute error code 4d21 I replaced the cooling fans (the upper one was totally burned out). Oven (13 years old) works like new now. Read More... 9 People found this story helpful Do-It-Yourself Rating: Repair Time Estimate: 1-2 hours Tools: Nut Drivers, Pliers, Screwdrivers