Q: What is My TPMS Light For?

Many modern day vehicles, especially ones manufactured after 2007, are equipped with a TPMS or tire pressure monitoring system. You will see a TPM system in vehicles manufactured before 2007, but this is the year it became mandated for all makes and models manufactured in the United States. This regulation came into effect as an attempt to make vehicles much safer and perform more efficiently.  As the title says, the TPMS is a system responsible for monitoring the vehicle’s tire pressure and has a function to alert the driver when the tire pressure falls below a predetermined value or a system malfunction has occurred. This is where the light on the dashboard instrument cluster comes into play.

Generally, the light will illuminate and stay on to alert the driver of a low tire or tires and will continue to do so until the fault which caused the light has been corrected. When the TPMS light illuminates, this is a signal to pull over when it is safe to do so and check your tire pressure. You would want to pull over preferably somewhere with an air pump unless you keep one in your vehicle. This is a good time to look over the tread for any punctures as a nail or road debris can most definitely cause an air leak. You may notice one or more tires may have a bulge where the rubber meets the road and this is a sign of low pressure. The low air pressure allows the metal wheel rim to travel dangerously close to the road. The TPMS light is a savior for many since the system can detect a low tire before it is completely flat and destroyed, as a tire without air can become severed by the metal wheel.

On another note, a flashing TPMS light may indicate a system fault. Say your TPMS light illuminates and starts flashing after you have checked all of your tires and you check once more to find that all are still inflated properly. In this case, some part of the TPM system has experienced a failure. You must hire your mechanic to inspect the system and unveil the fault which can be one or more of the tire pressure sensors.

Many vehicles have a sensor for each tire and can pinpoint the one that has lost pressure and these vehicles use a direct TPM system. The direct TPM system reads the actual tire pressure in each wheel within a small margin of error and reports back to the computer. Other vehicles use a different method to determine whether the tires may have lost pressure. This other method uses the wheel speed sensors of the vehicle’s anti-lock braking system to determine a flat tire and is called an indirect TPM system. When one tire has a lower pressure than the other, the circumference of the tire with less air becomes smaller and spins faster. The system can detect this situation and illuminate the tire pressure light. On a vehicle with indirect TPMS, an anti-lock braking system fault may have a negative effect on the TPM system.