My fuel economy seemed really strange lately and so I decided to check the ECU for any codes. While it wasn't on, the 0302 code was stored in the ECU. My main question is, is this normal? Can it be like the knock sensor and be stored but not be triggered until another event occurs? (Yes it does come back after resetting it, but only after city driving, if I drive on the freeway only it doesn't come back)

My other question is what should I check? I know the EGR system probably needs cleaned as the car has 145K on it and it hasn't been touched, along with the fact that it just barely passed smog when I got it tested a month or so ago. I did read though that this code does come up when cylinder 2 misfires. Do I need to check the coil, plug, and injector also? Also when I talked to the dealer they mentioned maybe O2 sensors need to be looked at. . . I got a code about a year ago for the right cylinder bank running lean, but that has never come back.

Any suggestions on this problem is greatly appreciated.

Summed up:
1. 0302 Code Stored, No CEL what does this mean?
2. What should I look at to prevent it from coming back?