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Getting to Know Your


How Does it work?

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It’s tough to determine if your tire’s air pressure is too low just by looking at it. In fact, if you can tell, chances are they need air as soon as possible. Fortunately, most cars today feature a tire pressure monitoring system (TPMS) to save us from getting a flat. TPMS acts as a safeguard, alerting you to low tire pressure and helping you to avoid potentially unsafe situations.

Aside from flickering on your dash, TPMS features tire pressure sensors which alert you when one or more of your tires is 25% under the recommended tire PSI (air pressure per square inch). It’s also important to know that there are two different kinds of TPMS technology today—indirect and direct. See below to learn more about these two technologies to better understand your car.

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Indirect TPMS

Indirect TPMS works with your car’s antilock braking system’s (ABS) wheel speed sensors. If a tire has low air pressure, it rolls at a different wheel speed than the other tires. An indirect TPMS does not actually measure tire pressure. Instead, it measures how fast your tires are rotating and sends signals to the computer that will actuate the indicator light when something in the rotation seems incorrect.


  • Inexpensive in comparison to the direct TPMS
  • Requires less programming and maintenance over time than direct TPMS
  • Less installation maintenance than its direct counterpart


  • May become inaccurate if you purchase a bigger or smaller tire
  • May be unreliable when tires are unevenly worn
  • Needs a reset after properly inflating every tire
  • Must be reset after routine tire rotation
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Direct TPMS

Direct TPMS uses a sensor mounted inside the wheel to measure air pressure in each tire. When air pressure drops 25% below the manufacturer’s recommended PSI level, the sensor transmits that information to your car’s computer system and triggers your dashboard indicator light.


  • Deliver actual tire pressure readings from inside the tire
  • Remains accurate, despite tire rotations or replacements
  • Simple resynchronization after tire rotation or tire replacements
  • Long lasting batteries (~10 years)
  • Typically included in a vehicle’s spare tire


  • Resynchronization can require costly tools
  • Battery is rarely serviceable—if the battery is drained then the whole sensor must be changed
  • These systems can make installation, service and replacement confusing for consumers and auto shops
  • Sensors are susceptible to damage during mounting and demounting

What Are The Benefits of TPMS?

TPMS notifies you when your vehicle’s tire pressure is low or is going flat. Properly inflated tires are critical to stability, traction, steering, handling and braking. When the air in your tires is low, they can affect your gas mileage and shorten your tire life due to uneven wear. More importantly, tires with low air can stress a tire to the point of failure, putting you and those on the road around you in jeopardy. Let Pep Boys make sure your TPMS is functioning properly with a checkup.

What Should I Do If My TPMS Light Turns On?

Check the air pressure in your tires and inflate any tire that is low— you can find your recommended tire pressure in your owner’s manual or in the doorjamb of your driver’s side door. The indicator should turn off once all of your tires are at the recommended PSI tire pressure rating.

Remember, TPMS is not a cure-all or a replacement for proper air pressure maintenance, it’s important to check your air pressure regularly, especially with extreme hot or cold weather. Vehicle aging and other factors can impact the system readings as well.

If you see your tire pressure light on, stop by your local Pep Boys for a free tire pressure check.