Yesterday my CHECK ENGINE light came on with code P1171 which means lean mixture while accelerating. At the time, I was in cruise control, not accelerating, but I was going up a steep hill. Today before I had a chance to disconnect the battery, the light went back out on its own. My question is whether these lights automatically reset themselves. I thought they had to be manually reset which would indicate that I may have a faulty lamp. Thanks in advance for any info.