The Toyota Prius Prime is one of the oldest plug-in hybrid electric vehicles (PHEVs) on the block. Given its near doubling of horsepower and its 6.6-second 0 to 60 mph time, the newer version is even more admirable. In a recent redesign, the hyper-efficient sedan may have lost its overly quirky looks, but if anything, even more love it now. In fact, owners say rodents lurking outdoors seem to love it too much.

Rodents love munching on the Prius Prime’s wiring

Rodents, you say? Yes, those furry, little woodland creatures you find in the oddest of places. For instance, in the wintertime, rodents of all sorts enter homes, garages, sheds, and typically wherever cars are stored to make a temporary shelter. Some know the sight of chewed-up newspaper inside a wheel arch or within the bowels of an engine, a rodent’s lair until it’s warm outside.

Unfortunately, the Toyota Prius Prime doesn’t just make a nice, secluded home for a rodent. It’s a food source. According to owner entries on CarComplaints, the number one issue reported with any year Toyota Prius Prime is “wires chewed by rodents.” But it’s not just happening to Primes; all vehicles with soy-based wiring insulation are at risk.

What is soy-based insulation?

Over the past decade or so, most auto manufacturers switched from petroleum-based plastics in their wiring covers to a more eco-friendly alternative. Traditional insulation contains carcinogens like formaldehyde and dozens of others. And the process of installing it on the wiring involves emitting hydrofluorocarbons—even more dangerous pollutants. In a step toward sustainability, automakers began using soy-based materials, decreasing production costs and being kinder to the environment.

Soy is like any other crop—a major food source for most of the world’s farm animals and various wild critters. As can be expected, mice, rats, squirrels, chipmunks, shrews, and others find it to be a tasty snack. Presumably, anything large enough to get underneath the car will likely find it a meal.

Is there a way to save your Prius Prime?

While we all can sit back and laugh about the Prius Prime being so good that its worst problem is rodents eating the wiring, it’s a serious issue. Some owners have had to spend thousands of dollars on repairing numerous electrical problems in their cars. While one may think such a widespread issue is covered under warranty, think again.

Toyota’s warranty specifically excludes damage from “environmental conditions,” among others. Such has been subject to multiple instances of judicial review in the unsuccessful class actions filed over the years. Toyota released a technical service bulletin for other models to alleviate the problems, only advising dealerships to use rodent-repellent tape when repairing cars with damaged soy-based insulation.

Whether you have a Toyota Prius Prime, another PHEV, or any other car, taking precautions during the colder months is important. Take the initiative to use repellant sprays and physical barriers to deter rodents from entering your vehicle’s undercarriage. Prime owners aren’t the only victims, and it’s simply a cost of sustainability.