Modern cars have loads of features that make keeping up with maintenance easier than ever before. There are sensors and warning lights for nearly everything, so repairs take you by surprise less often than with older cars. However, for these fantastic new features to continue to work, the sensors and components that collect the data need to stay operational. Auto repair looks different than it did in the past, and understanding these intricate parts is crucial. In this blog, we’re going to look at tire pressure monitoring systems (TPMS), the different types, and how they work.
There are two main types of TPMS. Here’s a look at how they monitor your tire pressure.
Direct TPMS
A direct TPMS uses sensors located inside each tire to monitor the pressure. They are usually attached to the valve system or integrated into the tire’s assembly. Because the sensors are inside the tire, they can continuously monitor the pressure and send real-time data to the control module. The TPMS control module or vehicle’s onboard computer then receives the data from the sensors as radio frequency signals. If the sensors detect that the tire pressure is either higher or lower than the correct level, the TPMS control module triggers the dashboard warning light. Because there is a sensor in each tire, the onboard computer can tell you exactly which tire is over or under-inflated.
Indirect TPMS
An indirect TPMS is more common because it uses other systems in the vehicle to determine if the tire is properly inflated. The indirect TPMS is integrated into the anti-lock braking system (ABS) to monitor the tire pressure indirectly. ABS uses wheel speed sensors to determine if the wheels are locking up, and the TPMS uses the same sensors to measure the rotational speed of each wheel. When a tire loses or increases tire pressure, its rolling diameter changes, which varies the wheel speed. The TPMS control module compares the wheel speeds to estimate if any of the tires are over or under-inflated. If the wheel sensors detect a significant difference in wheel speed, the TPMS triggers the dashboard warning light.
Indirect TPMS can sometimes indicate a problem with the tire pressure when there isn’t. This happens when errors build up until the sensors think the tire is rotating at the wrong speed.
