Smart Fortwo Turbo Failure Causes Multiple Issues

Having some experience with turbo-related issues, I encountered a very similar problem with my Smart ForFour diesel (2012). The symptoms were almost identical, engine warning light, power drops, and that characteristic whistling noise from the turbo system. The boost sensor was indeed causing these issues. In my case, the main problem was a damaged wiring connection to the turbo boost pressure sensor. The intake manifold was functioning correctly, but the faulty connection was sending incorrect readings to the engine management system. The repair process was straightforward: Full diagnostic scan, Testing of the turbo system components, Repair of the cable connection to the pressure sensor, Final testing of boost levels Total cost was 95€ for the diagnostic work and cable repair. Before suggesting more specific solutions, could you provide: Current mileage, Any recent repairs or maintenance, Whether the check engine light shows constant or intermittent, Description of driving conditions when symptoms occur most, Any unusual sounds from the engine bay area This information would help determine if your issue is identical to what I experienced or if there might be additional concerns with your turbo system that need addressing.

Thanks for following up. Mileage is currently at 150642 KM since the last inspection. The check engine light is constant, not blinking. Symptoms are most noticeable during acceleration and cold starts. The whistling noise from the turbocharger area gets particularly loud when going uphill or under heavy load. I checked for boost leaks around the intake manifold and turbo system connections but found no obvious signs. However, the turbo pressure sensor connector does look a bit corroded. This makes me think your suggestion about the wiring issue could be spot on. The most recent service was just an oil change about 1500 KM ago. No other repairs have been done to the turbo system or engine components recently.

Based on your description, especially the corroded sensor connector, this definitely sounds like the same issue I faced. The symptoms match exactly what happened with my Smart ForFour, particularly that loud whistling from the turbocharger area during heavy load. After getting my wiring issue fixed, I also had the technician clean and protect the connector area to prevent future corrosion. One thing I learned is that the turbo boost connections are particularly sensitive to corrosion, which can cause erratic readings in the air intake system. For reference, my repair expanded to include: Cleaning of the turbo boost sensor connector, Application of dielectric grease, Testing of all intake manifold connections, Verification of proper boost pressure levels Total cost increased to 140€ with these additional steps, but it completely resolved the issues. The engine regained full power, fuel consumption returned to normal, and all the problematic symptoms disappeared. Given the similarity of our cases and the visible corrosion you mentioned, I strongly recommend having the connector cleaned and sealed properly rather than just fixing the immediate wiring problem. This preventive step saved me from recurring issues with the turbo system.

Thanks everyone for the helpful responses. I've decided to take my Smart to the shop tomorrow and have them specifically check the turbo boost pressure sensor connections. The corrosion issue seems very likely given the symptoms and your similar experience. Going to ask them to do a full inspection of the intake manifold and turbocharger system while they're at it, just to be safe. The check engine light and performance issues are too similar to your case to ignore. If it ends up being mainly connector-related and costs around 140€ for the complete fix, that would be a relief compared to what I was fearing might be wrong with the turbo itself. Will update once I get the diagnosis and repair completed. Really appreciate the detailed information about the repair steps and costs, gives me a good baseline when discussing it with the workshop.