Toyota Repair: po138 and po606, scion tc, oxygen sensor

Question
Ted,
 I own a '05 scion TC, which as you probably know has the 2.4 liter camry engine.Late this summer I came back from a week long trip to Florida and when I started my car up and my check engine light was on. As soon as i got home I had the codes checked and it was the po138(o2 sensor) and po606(pcm failure. Before I was able to make the appointment at the dealership the light went off. I figured it was a fluke. 2 1/2 months later it came on again and the same codes we given. Once again it went off. it is now back on. I have an scheduled service. The 3 times it came on was after start up and not while driving. Once was after sitting for a week and the other two times after sitting overnight in our fine New England winter weather. Does this have something to do with the weather and sitting and our the two codes mutually exclusive of each other. Your input would be appreciated.

Answer
The p0138 code indicates a #2 oxygen sensor failure, it's the one behind the cat converter. The warranty is good for 3yrs/50,000 miles in some states, check with the dealer, the p0606 is an internal ECM malfunction, it should be replaced, it's warranty period is 8yrs/80,000 miles.