Smart Fortwo Tire Pressure Warning Light Stays On

Common Causes for the Tire Pressure Warning Light in Your Smart Fortwo and How to Resolve Them

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Reviewed by
Devin Cabugcal
Written by RepairPal Car Genius
Updated January 14, 2025
0%
40% chance it's the
Tire Leaking Air
0%
30% chance it's the
Wheel Leaking Air
0%
15% chance it's the
Tire Pressure Monitoring System
0%
15% chance it's
Something else
The most common reasons a Smart Fortwo tire pressure warning light stays on are a leaking tire, a wheel that no longer holds air, or a faulty tire pressure monitoring system.
  • Tire Leaking Air: A puncture, valve stem issue, or rim damage can cause a tire to leak air, leading to loss of pressure.
  • Wheel Leaking Air: A puncture or damage to the tire or rim can cause air to leak, resulting in a loss of tire pressure.
  • Tire Pressure Monitoring System: A malfunctioning tire pressure monitoring system can be caused by faulty sensors or a dead battery in the sensor units.
Proper diagnosis will determine the exact cause of your symptom, saving you money on unnecessary repairs. The diagnostic experts at RepairPal Certified shops have the right tools and experience to solve any symptom.

How much does it cost to fix a Smart Fortwo tire pressure warning light stays on?

Common Repairs

The total repair cost will vary based on the condition of your vehicle and the number of repairs needed to fix your symptom. Proper diagnosis will save you money by finding the exact repairs needed to fix your car right the first time.

When a tire pressure monitoring sensor fails, the tire pressure monitoring system control module will recognize a loss in communication and turn on the warning lamp which indicates the failure. This is most often the case. However, the tire pressure monitoring sensor may also fail by reporting incorrect tire pressures. This could cause a flat tire to go unrecognized, or a properly inflated tire to signal a low or high tire pressure warning.

When a relearn is needed, for any reason, the TPMS warning light will illuminate, and many vehicles will display a message relating to the TPMS system being inoperative or loosing communication. It is important to keep a watchful eye on tire pressures when this system is having issues because there is no warning available for underinflation or overinflation of the tires.

Wheels offer very few symptoms, but these symptoms should never be ignored. Visible cracks on the wheels may appear, especially after hitting a large bump, Most often, this will also be accompanied by loss of air from the tire on that wheel. Also, vibration in the steering wheel is very common when the tire is out of balance, and improper wheel nuts or bolts can cause creaking and popping noises to develop. Again, there are very few symptoms, but they should not be ignored.

The only symptoms of a TPMS control module failure are failing to alert the driver of underinflation or overinflation of one or more tires, failure to communicate with the body control module or TPMS sensors, or erroneously reporting incorrect tire pressure.

The only symptoms requiring diagnosis for the tire pressure monitoring system warning lamp is if the warning lamp has illuminated while the tires have correct air pressure, or if the air pressure for the tires is out of specification and the warning lamp is off. This is because the overwhelming majority of cases where the TPMS lamp illuminates is due to the change in ambient temperature.

Troubleshooting Tire Pressure Warning Light in a Smart Fortwo

When addressing the tire pressure warning light in your Smart Fortwo, start with the most straightforward solution: checking the tire pressure. Use a reliable pressure gauge to ensure that each tire is inflated to the recommended levels, typically between 1.8 to 2.5 bar. If the pressure is off, adjust it accordingly, as this alone may resolve the warning light issue. If the tire pressure is correct, the next step is to reset the Tire Pressure Monitoring System (TPMS). Depending on your model year, this may involve pressing a reset button on the dashboard or navigating through the vehicle's menu as outlined in the owner's manual. For those with an indirect TPMS, you might need a diagnostic tool or a magnet to reset the system, which can often be done at home with the right equipment. Lastly, always inspect your tires for any visible damage or irregularities before concluding the troubleshooting process. By following this methodical approach, you can effectively manage the tire pressure warning light and maintain your vehicle's safety and performance.

Troubleshooting Tire Pressure Warning Light in a Smart Fortwo

When dealing with the tire pressure warning light in your Smart Fortwo, it's essential to understand the common problems that may trigger this alert. One frequent issue is simply low tire pressure, which can occur due to temperature changes or slow leaks. Always start by checking the pressure in all tires, ensuring they are inflated to the recommended levels indicated on the driver's side door pillar. If the pressure is correct but the light remains on, the problem may lie with the tire pressure monitoring system (TPMS) itself. This could involve malfunctioning sensors, which may require resetting. Depending on whether your vehicle uses a direct or indirect TPMS, the reset process can vary significantly. For direct systems, a simple button push or menu navigation may suffice, while indirect systems might necessitate specialized tools or dealer assistance. Additionally, physical tire damage, such as punctures or sidewall issues, can also cause the warning light to activate. Regularly inspecting your tires for visible damage and ensuring they are in good condition can help prevent unnecessary alerts. If you've addressed these common issues and the warning light persists, it may indicate a deeper problem within the TPMS, warranting professional evaluation.

Why is the Tire Pressure Warning Light Staying On in a Smart Fortwo?

When the Tire Pressure Warning Light remains illuminated in your Smart Fortwo, it is crucial to address the issue without delay. Ignoring this warning can lead to serious safety risks, such as reduced vehicle stability and increased stopping distances, which can compromise your ability to control the car effectively. Additionally, driving on under-inflated tires can cause uneven tire wear, leading to costly replacements and potential damage to the wheel rims. The Tire Pressure Monitoring System (TPMS) is designed to alert you to these critical issues, and if the light stays on, it may indicate a leaking tire, a malfunctioning TPMS, or incorrect tire pressure. To ensure your safety and the longevity of your vehicle, take the time to check your tire pressure against the manufacturer's specifications, which can usually be found on a sticker inside the driver's side door. If necessary, reset the TPMS following the appropriate steps, as this can help restore normal function and provide peace of mind while driving. Addressing these concerns promptly not only enhances your safety but also helps maintain the overall performance of your Smart Fortwo.

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