This truck is a 2018 nissan frontier that has ~10k miles and is driven daily. in the evenings it is kept outside. recently, a horrible odor began coming from the ventilation system. i immediately started dismantling the passenger dash, removed the cabin air filters, and discovered a dead mother rat and 4 offspring in the compartment above the filters. if i had not been able to find the problem, the truck would have been completely unusable. how were they able to gain entry? i am guessing through some fresh air intake that is obviously open to the exterior. nissan needs to add a very simple wire mesh cover to the offending entrance. to allow access to a fully grown rat, it is assuredly 2-3" in diameter! thankfully, i was able to catch the problem. however, it is summer, high temperatures, and had the truck been left unattended for several days, the resulting odor may have never been remediated. my concern is, if i can't find and cover the opening, this could happen again.