Under the Transportation Recall Enhancement, Accountability and Documentation Act (TREAD) after 2008 flat tire light is required on all new cars. This system alerts the driver if the tire pressure in any of the four tires drops 25 percent or more. Some systems will trigger the tire pressure light if the tire pressure is too high. Congress took the Act because of an increasing number related to tire problems highway accidents. Studies have shown that up to 75 percent of drivers have no idea about their tires pressure in.
When the flat tire light comes and stays on – it looks like one of your tires (at least) is under-inflated. The issue is that most of TPMS doesn’t tell you which of your tires is under-inflated meaning you have to check each tire to figure out which one is low, and then add air. Sometimes it is impossible or difficult to tell simply by looking at the tire. Furthermore, car on a slope can have a normal tire that appears low on pressure.
In many cases, flat tire light can make some unnecessary troubles. It can trigger soon after the car was serviced for a tire rotation, brake system work, a CV boot/axle replacement – then it’s likely that something was tripped tire pressure sensors, which lighted the warning light.
Most annoying when the tires are checked and pumped up, but the tire pressure light does not disappear. In that cases, you require a reset procedure (here is an example for Honda Accord) that must be performed.