Smart Forfour Throttle Sensor Causing Power Loss Issues

I had a very similar issue with my 2016 Smart Fortwo last winter. With moderate experience working on cars, I initially thought it was just a dirty throttle body causing poor air flow, but the symptoms matched what you describe, sluggish acceleration and the check engine light came on. The car went into limp mode several times, especially during acceleration. After taking it to the workshop, they diagnosed a faulty accelerator pedal position sensor. The entire pedal module needed replacement due to failed internal electronics. Total repair cost was 265€ including diagnostic and labor. The good news, it was a relatively quick fix, taking about 2 hours once they had the part. Fuel efficiency and throttle response returned to normal immediately after the repair. To better assist with your situation, could you share: Any diagnostic codes from the check engine light, Whether the car goes into limp mode, If the issue happens more when the engine is cold or warm, Current mileage on your Forfour These details would help confirm if your issue matches what I experienced.

Yes, I experienced the same behavior recently at 131239 KM. After reading your response, I checked the air intake system more closely. The throttle body response definitely matches what you described, sluggish acceleration and delayed throttle response, particularly noticeable during warm-up. My check engine light showed P0121 and P0122 codes, which point toward throttle position sensor circuit issues. The limp mode activated twice last week during highway merging. Interesting that your repair cost was only 265€. The quote I received was significantly higher at 390€ for parts and labor. Might get a second opinion since the symptoms are nearly identical to your case. Just had my regular service done last month, so the basic maintenance items are all current. Did you notice any warning signs before the complete failure?

Thanks for those additional details. Yes, I noticed some warning signs about 2-3 weeks before the complete failure in my Smart Fortwo. The throttle sensor issues started subtly, occasional hesitation during cold starts and minor engine idling fluctuations, especially on damp mornings. Those P0121 and P0122 codes are exactly what my car showed. The 390€ quote does seem high compared to my repair cost, but prices have increased quite a bit since my repair last winter. Still, getting a second opinion is smart since throttle sensor replacement costs can vary significantly between shops. A crucial detail I forgot to mention: after the repair, I learned that corroded wiring connections had contributed to the sensor malfunction. The workshop cleaned and sealed the connections as part of the fix, which might explain why I haven't had any check engine warnings since. Given your mileage is close to what mine was (I was at about 128000 km), and the identical error codes, I am even more convinced you are dealing with the same issue. Make sure any shop that does the work includes checking the wiring harness connections to prevent a repeat failure.

The symptoms match exactly what you both experienced, definitely going to check those wiring connections. The check engine light codes being identical really confirms it. Just called another repair shop and got quoted 310€ for the complete job including diagnostics and labor, which sounds more reasonable. Really helpful to know about the gradual onset of symptoms too. Looking back, I did notice slight hesitation during cold starts about a month ago but dismissed it. Should have paid more attention to those early warning signs. At least now I know what to watch for in the future. Going to schedule the throttle sensor replacement for next week. Will make sure they inspect the entire air intake system and clean those wiring connections while they are at it. The fuel efficiency has taken a real hit lately, so fixing this should help get that back to normal too. Thanks for sharing your experience, saved me from potentially overpaying and helped pinpoint the exact issue. Will update once the repair is done to confirm if it fully resolves the problems.