Why is the tire pressure light on but the tires are fine?
3 Answers
The reason the tire pressure light is on but the tires are fine could be due to overinflated tires or driving with low tire pressure for an extended period. Here are the details: 1. Overinflated tires: If the tire pressure monitoring light comes on due to a punctured tire, it usually indicates a very slow leak, which can be checked with a tire pressure gauge. Sometimes, the light may come on because the tire pressure is too high. According to the international standard GBT2978-2008, the recommended inflation pressure for passenger car tires is as follows: standard tires: 2.4-2.5 bar; reinforced tires: 2.8-2.9 bar; maximum pressure: should not exceed 3.5 bar. Therefore, if any tire exceeds 3.0 bar, it may trigger the tire pressure monitoring light. 2. Driving with low tire pressure: The tire pressure monitoring light may also come on if you drive with low tire pressure for too long. This usually happens when one tire has significantly lower pressure, causing it to heat up during high-speed driving, which in turn increases the tire pressure. In such cases, you should stop and rest or replace the tire with a spare one.
I was startled by a tire pressure warning during a long-distance drive. After stopping to check, all four tires seemed fine. Later, a mechanic used a tire pressure gauge and found that the sudden temperature drop had caused the tire pressure to be generally 0.2 bar lower. The mechanic said the tire pressure monitoring system is quite sensitive, especially during seasonal transitions in autumn and winter, where thermal expansion and contraction can cause a difference of about 0.3 bar. He recommended checking the tire pressure monthly when the car is cold and adjusting it according to the values on the door frame label. Don’t forget the spare tire sensor either—last time I didn’t reset the system after changing a tire, and the warning light stayed on for two days. Now I’ve learned my lesson and always keep a portable air pump in the car. If the tire pressure seems off, I inflate it first and observe. If the alarm persists, then it’s time for a proper check-up.
Last month, my tire pressure warning light suddenly turned yellow, even though the tires weren't flat. After half an hour of inspection at the 4S shop, they found mud caked on the wheel speed sensor. The technician explained that this indirect tire pressure monitoring system relies on wheel speed differences to detect issues, and a tread depth variation of over 1.5mm between tires can trigger false alarms. They also taught me a self-check method: first measure the actual tire pressure, and if it's normal, long-press the tire pressure reset button on the center console. If the light remains on after driving two kilometers, then check the wiring, paying special attention to the sensor battery which tends to lose charge after five years. Always remind the mechanic to use special tools to reset the sensors after tire repairs - last time at a roadside shop they failed to properly reset mine after fixing a puncture.
