2005 Suburban Z71 with a 5.3. The code is Evap large leak detected. Reasonably sure it is not the gas cap. I replaced it with a brand new AC Delco part, because the rubber was showing some signs of wear. The code is on its way back (has not set the check engine light, but has put a message in the information center to check gas cap). I've looked at all the rubber tubing I can see easily in the vicinity of the rear axle and filler neck from underneath. I do not see anything amiss. There are no other codes set or pending.