Smart ForFour Suspension Failure, Fix Guide & Symptoms

I had a similar issue with my 2003 Smart Fortwo last year, so I have some experience with this type of suspension problem. The symptoms you describe match what I encountered, poor ride comfort and vehicle suspension warning lights. In my case, the damping control system was showing errors due to a faulty wiring connection at the shock absorber sensor. The workshop found that the cable had worn through due to constant movement, causing intermittent connection issues. After a thorough diagnostic check, they repaired the damaged wiring and replaced one connector, which resolved the problem completely. The total repair cost was 95€. Car handling returned to normal immediately after the fix, and the warning lights disappeared. However, to provide more specific advice for your situation, could you share: 1. Current mileage on your Forfour? 2. Did the issue start suddenly or develop gradually? 3. Does the problem seem worse on one side of the vehicle? 4. Are there any unusual noises when driving over bumps? This information would help determine if your issue is similar to what I experienced or if it might be related to other suspension components.

I have 116526 KM on the odometer and the issue started gradually over the past few weeks. The problem seems evenly distributed on both sides. When driving over bumps, there is a slight knocking sound from the front suspension. The damping control warning persists even after clearing the error codes. The vehicle suspension feels particularly stiff over small bumps, almost like the shock absorbers are not functioning properly. The car handling has become unpredictable, especially during cornering. Last service was done 3 months ago but it only included basic maintenance like oil and filters, no suspension work was performed. Based on your experience with the wiring issue, I will have the workshop check the sensor connections first before considering full shock absorber replacement.

Thanks for providing those additional details about your Forfour. After reading your description, I suspect your issue might be more extensive than the wiring problem I encountered on my Smart. The knocking sound combined with stiff ride comfort and persistent damping control warnings suggests possible wear in the active suspension components. When my car developed similar suspension failure symptoms, I initially also thought it was just sensor related. However, the stiff ride and knocking sounds you describe remind me of when my shock absorbers eventually needed replacement a few months after the initial wiring fix. In your case, given the mileage and symptoms, I would recommend: 1. Having the entire suspension system inspected, particularly the shock absorber units 2. Testing the damping control module functionality 3. Checking all suspension mounting points for wear For reference, when I needed full replacement of both front shock absorbers with new damping control sensors, the total cost was around 850€. The improved car handling and ride comfort after replacement was dramatic. Would you be able to describe if the knocking sound changes intensity at different speeds? This could help pinpoint whether the issue is primarily in the shock absorbers or if other suspension components are involved.

Thanks for all the helpful input. The knocking sound definitely gets louder at higher speeds and is most noticeable between 60-80 km/h. After hearing about your experience, I scheduled a full suspension system inspection for next week. I agree the symptoms point to worn shock absorbers rather than just a sensor issue. The combination of stiff ride, persistent damping control warnings, and that speed-dependent knocking sound matches what you described from your experience with failed shock absorbers. My mechanic quoted around 900€ for replacing both front shock absorbers including new sensors, which seems in line with what you paid. While its not cheap, the unpredictable car handling and poor ride comfort make it worth fixing properly. Will post an update once the workshop completes the inspection and confirms if the suspension failure is indeed caused by worn shock absorbers or other issues with the damping control system.