So my truck is a 95 k1500 350 tbi. Code 13 popped up a week ago which is o2 sensor. The truck ran great no problem just a shaky idle but the rpms didn't jump or anything. I changed the sensor cuz my OCD about the engine light. Left the battery disconnected all night reconnected it this morning cranked it no engine light. 10 seconds later it pops up. Why is it still on?