headlights throwin a code???

my service vehicle soon light comes on almost every time it gets dark or it rains. i came to the conclusion that it has to do with the daytime running lights or headlights. can DRL throw codes? if so, how can i trouble shoot it to get it fixed. car runs normal and everything, just kinda annoying. Also i hammered on the throttle and the battery light came on, so it could be somethin with the alternater too. i know its not the battery, as i got a brand new yellow top. the lights dont dim or anything, and sometimes the SVS light is off if i shut the car off/on.