Code P0300 P0301 P0302

I left my 2008 Prius (215K miles) unused for a week before the Christmas holidays. When I started the car upon my return, there was an audible misfire for about 10 seconds and then the engine seemed to fire properly. I have a ScanGuage II attached and it showed me the codes P0300 P0301 P0302. I cleared the codes to see if the problem would occur again but everything seems ok thus far (I may have driven the car for 30 miles during the holidays since I first observed the codes). I drive 80 miles a day commuting to work and would like some advice from this forum on any preventive care I can do to prevent code p0300 again. I have changed sparks (oem NGK), both water pumps, coolant, Trans fluid and serpentine belt around 180K miles. I get over 50 MPG in summer and about 46 MPG in winter, in central Jersey. I am still running on the original hybrid and 12V batteries. I monitor both batteries when I drive and they seem to be holding up well. The hybrid battery maintains a charge around 60% while driving and the 12V hovers between 13 and 14 volts when driving. If changing the 12 volt is recommended, should I go for the Optima? My local dealer recommends another brand which seems a bit cheaper than the Optima. I forget the brand but the dealer says it is not OEM.

 

Thanks, I will check the wires. I normally park the car outside but had it parked inside my garage when I went out of town. I have cleared the codes and they have not appeared again, as yet.

 

It's been a month since I cleared the codes P0300 P0301 P0302, and I haven't seen any error codes in my scanguage2 so far. I am averaging 47mpg which is my typical average every winter. Hopefully it means my wires are OK. I would still like to change my 12V battery given its age. Any recommendations please? My original still shows a steady 13.7V when running. I have not measured the voltage before turning the car on.

 

Thanks ! Ironically, I park my car in the driveway rain or snow. This one time when I parked the car inside the garage and went out of town for a week, it acted up on my return. My local Pep Boys in NJ has "Optima Yellowtop Prius Deep Cycle Car Battery, Group Size DS46B24R" for $238. Has anyone had issues with this Optima on a Gen II? I have yet to check with my local dealer. If I can give my friendly local auto store my business, I'd like to try the Optima.