Why does the tire warning light come on?

Why does your Lexus have this system?

Tire pressure sensors or tire pressure monitoring systems have been required by law on all light vehicles (under 10,000 pounds) manufactured after September 2007. The law was in response to the Firestone tire recall of the mid 1990s. Tire pressure monitoring systems aren't new, the technology first appeared usually in higher priced European luxury models around 1986. It soon after that, the systems started to appear in luxury models across the globe. In addition to the safety aspect of having properly inflated tires, there are also potential fuel savings from lower rolling resistance.

 

The Tire Pressure Monitoring System (TPMS)

The most common tire pressure sensor is a battery powered DIRECT sensor (meaning it is directly mounted with the wheel and tire). It uses a radio frequency to transmit data to the instrument cluster computer in the vehicles. Usually as long as the tires are within a certain pressure range of each other, the system is set.

 

However, if one or more tires loses or gains more than a certain amount of pressure (about 20 percent to 30 percent of air pressure difference between the others) it will trigger the instrument cluster panel and set off a warning indicator light or a "low tire pressure" light. In some vehicles, there may even be an information center which will display each individual tire's air pressure.

 

Located on the driver's side door frame is a label with the manufacturer's recommended tire pressures for front and rear tires. While this is a guideline for air inflation, the system doesn't necessarily fault if the recommended tire pressure varies as long as all the tires have the same amount of air in them. It is important to note that some vehicles that have full-size spare tires may also have a sensor in the spare that is also monitored. Once a low tire or flat tire is detected, the dashboard warning light will illuminate and stay on until the tire has been repaired or replaced. Some tire sensor systems need to be reset after such a situation.

 

The battery powered sensors are somewhat bulky and heavier than a standard valve stem, plus the batteries do exhaust after some time. Improper tire replacement can also damage the TPMS sensor and affect the wheel balance if replacement is not performed by knowledgeable installers such as our factory trained technicians. If damaged, the replacement of the sensor is quite costly.

 

What can you do?

Just like helium balloons, over time tires loose some air pressure through microscopic pores in the rubber. It is common during winter months when the air temperature drops for tire air pressures to drop. Lexus recommends a monthly inspection of all the tire pressures. This is a simple process and only requires an inexpensive tire pressure gauge similar to this:

 

 

When performing the tire pressure inspection, it is best when the tires are cold, since driving on them warms up the tire and the air pressure rises slightly. Just twist off the cap on the tire valve stem and press the inlet part onto the exposed tire stem. The gauge will pop out showing the relative tire air pressure.

 

Here at Lexus of Pleasanton, we routinely inspect the tire pressures with all in shop services. This not only prevents abnormal wear on the tires but potentially saves fuel and reduces exhaust emissions from a more efficient engine. So everyone benefits from this simple inspection.

Feel free to contact your Sales Consultant or any of our Service Advisors if there are any questions regarding tire air pressure check or the TPMS warning light.