So this morning I went outside to warm up My HHR since it was 2 degrees outside. Started fine and everything seemed happy. came out 10 minutes later to go to work and the check engine light was on....... With no choice I drove off to my destination and the HHR seemed like it was running fine. Later in the day was able to stop by a Autozone and had the HHR scanned and found code P0304 miss fire on Cyl #4. The HHR didnt feel like it was missing so I had them clear the code. The light has stayed off and has not come back on. so my question is this , could this just be a fluke? should I be concerned?
2007 2LT 2.4 5-Speed 50,000 miles

 

I wouldn't get too worried yet cold weather has some strange effects on eletronics. If the code returns then you will need to get it checked out. fuel system cleaner wouldn't hurt.