The ignomious CHECK ENGINE light on my car (Mazda 3) engaged on a road trip last weekend. I suspected that this was due to a lost gas cap (lanyard on the original broke off some time ago) which I confirmed.
Read a few codes at an auto zone on the way back and they said 3 codes relating to the evaporative emissions system - recommended a new fuel pump. Yeah, right. Bought a new gas cap and returned home without incident.
Said light did not extinguish after 300 miles of highway driving, so I used the DMS code scanner to delete codes. Conveniently, this extinguished the bleeping light. I’ll run it again in a few days to see if there are any lingering alarms, but I suspect it threw those for lack of a means to tell.me the gas cap was missing.