Technician A states that the indirect tire-pressure monitoring system was used before the 2008 model year. Technician B claims it compares the rotating speeds of different tires. Which technician is correct?

The correct answer is that both technicians are right. The indirect tire-pressure monitoring system (TPMS) was indeed utilized in vehicles before the 2008 model year. This type of system does not rely on pressure sensors inside the tires but instead estimates tire pressure by monitoring the wheel speed of each tire.

Technician B's statement is also accurate; the indirect TPMS compares the rotating speeds of the tires. When a tire is under-inflated, its overall diameter decreases, causing it to rotate at a different speed compared to the properly inflated tires. By analyzing these differences in rotational speed, the system can identify which tire may have low pressure.

Together, both technicians provide valid information about the characteristics and functionality of the indirect tire-pressure monitoring system.