[Ross] has a 2008 Toyota Tacoma. Like many late model cars, each tire contains a direct tire pressure monitoring sensor or TPMS that wirelessly sends data about the tire status to the car. However, unlike some cars, the system has exactly one notification to the driver: one of your tires is low. It doesn’t tell you which one. Sure, you can check each tire, but [Ross] had a different problem. One sensor was bad and he had no way to know which one it was. He didn’t have any equipment to test the sensor, but he did have an RTL-SDR dongle and some know-how to figure out how to listen in on the sensors.
The key was to use some software called RTL-433 that is made to pick up these kinds of signals. It is available for Linux, Windows, or Mac, and supports hundreds of wireless sensors ranging from X10 RF to KlikAanKlikUit wireless switches.