check engine light flashes and getting a cyclinder 3 misfire code on tester. on 2003 Toyota Tundra

what is the most common cause?

Asked by for the 2003 Toyota Tundra
Always good to post engine size, two options!! Here goes,(COP) Coil On Plug defective # 3 cylinder.
You are right, I should have included engine size in my query. I meant to do so, but forgot. My engine is the I-Force 4.7l v8 DOHC. Thanks ever so much for your prompt reply. Upon doing some further research, it would seem that the COP is a common fault with these engines. I will do as you suggest and replace the coil. Also, since it has been close to 40,000 miles since my last plug change, I will replace all spark plugs.
Thanks again for your response. I will post results of the above corrections.
Sounds good!