SES P0306 came and gone need advice

[jc1surf]

hi guys, thanks in advance to all advice and answers.
so the other day the infamous SES light came on. The following night, I pumped gas, viola, ses light goes away immediately after i started engine.

i finally ran the OBD, and got P0306 cylinder 6 misfire powertrain.
what does this mean? there was a little vibration and shaking right when i started engine. i turned off engine and restart engine, no shaking, but SES remained on.

so the day before i was installed the carrier, couldn't get it aligned correct so had to drive with panel off: door locks wouldnt work and "door open" message was on. next day was able to finish up the carrier. As advised by other member, i put key ON position to reset the switchs/key fob/ alarm...all worked as normal perfect. then I go and replace the front windshield washer pump. I did not remove the tank out of the engine. I just loosened the two bolts and then replaced the pump and yup, fluid was gushing eveywhere where the washer tank is located. so that's done. im all happy with new door carrier and finally front windshild washer working. then turn on engine and dreaded SES came on.
i didnt notice any change in power/acceleration/rpm spike while driving. I have not had a change to run the OBD coder yet. Next night i pump gas, and it was gone.
So i am wondering what you Xperts think it might be. Sorry for the long story, just thought i'd add that part in since it was my first DIY project if it had any relation to the SES. should i run the obd coder to see if anything got stored into memory.?

thanks again