Smart TPMS Sensor Issues: Causes and Quick Fixes

Having dealt with a similar tire pressure warning issue on my 2013 Smart ForFour Electric, I can share my experience. I have some experience working on EVs and tire pressure monitoring systems. The low tire warning kept appearing despite correct tire pressure levels. After checking each tire with a pressure gauge multiple times, the readings were all correct, but the system continued showing warnings. The issue turned out to be depleted TPMS sensor batteries. These sensors are built into the tire valve stems and communicate wirelessly with the car. When their batteries die, they can trigger false low tire pressure warnings. My repair shop diagnosed the problem and replaced all four TPMS sensors. Total cost was 280€ for parts and labor. The warning lights disappeared immediately after the repair and have not returned. To better assist with your specific case, could you share: Have you manually checked the tire pressure recently? Does the warning come on while driving or only at startup? Are you getting warnings for specific tires or all of them? Have you had any tire work done recently? Regular tire checks are important, so even with a faulty sensor, keep monitoring your tire pressure manually until the system is fixed.

Thanks for the detailed response. My Smart currently shows 194855 KM on the odometer. I checked each tire with a reliable pressure gauge yesterday and they were all at the recommended PSI. The sensor fault warning appears while driving, usually after about 15-20 minutes on the road. Its happening on all four tires intermittently. The tire check I performed suggests the actual pressures are fine, which makes me think the TPMS sensors are the culprit. I did have two flat tire repairs about 6 months ago, but the warnings only started recently. Given the age of the car and your similar experience, I suspect the sensor batteries might indeed be failing. Will probably need to get all sensors replaced to properly fix the tire inflation monitoring system. The 280€ cost reference is helpful for budgeting. Will contact my regular shop to check their pricing for a full TPMS sensor replacement.

This definitely matches my experience with the Smart ForFour, those TPMS sensor batteries typically last 5-7 years before failing. With your odometer reading and the fact that the air valve sensors are likely original, a full replacement makes sense. The intermittent warnings during driving are a classic sign of failing TPMS sensors. While the flat tire repairs could have impacted the sensors, the timing suggests its more likely related to battery depletion. Since posting my earlier reply, I actually had another sensor fault on my rear right tire last month. The repair shop found that one sensor had completely failed while the others were showing weak signals. They suggested replacing all four to avoid future issues. A quick tip before you visit the shop, have them verify the sensor fault with their diagnostic tool. Sometimes the TPMS issue can be resolved with a simple recalibration, though given the age of your sensors, replacement is likely needed. The current market price for a full set remains similar to what I paid. Most shops charge between 250-300€ for all four sensors including labor. Just make sure they use OEM-quality parts compatible with your specific model year.

Thanks for the advice. After taking my Smart to the shop, they confirmed what you suggested, failing TPMS sensors were causing the tire pressure warning lights. Their diagnostic scan showed weak signals from all sensors. The repair cost came in at 295€ for replacing all four air valve sensors. A bit more than expected but worth fixing properly. They used OEM-compatible sensors with fresh batteries that should last another 5-7 years. After the replacement, the sensor fault warnings completely disappeared. The tire pressure monitoring is now working correctly again. For anyone else facing similar TPMS issues on an older Smart car, checking the sensor batteries is definitely the first thing to investigate. Really appreciate the help in diagnosing the problem. Having accurate tire pressure monitoring gives great peace of mind, especially given how important proper tire inflation is for safety and efficiency.