Smart Fortwo Parking Assist System Failure Fix Tips

I had a similar issue with my Smart Forfour (2004) where the parking assist system failed completely. Having some experience with basic car electronics, I first tried the usual checks like you did with the fuses. The fault turned out to be faulty wiring, specifically a damaged cable connection to one of the rear parking sensors. The constant exposure to weather and road debris had worn through the protective covering, causing intermittent failures before the system stopped completely. Took it to a workshop where they diagnosed the issue using proper diagnostic equipment. They found corroded plug connections affecting the entire parking assist system. The repair involved replacing some wiring harnesses and properly sealing the connections. Total cost was 95€ and the parking sensors have worked flawlessly since. To help troubleshoot your specific case better, could you share: Are there any visible damages to the radar sensors? Does the rearview camera still work if equipped? When did the issue start, suddenly or gradually? Any recent car washes or weather exposure that might have affected the system? This sounds very similar to my experience, but knowing these details would help determine if its the same root cause.

Last service was at 185000 KM, so pretty recent. Thanks for the detailed response. Mine seems a bit different, all ultrasonic sensors appear physically intact with no visible damage. The rearview camera actually still works perfectly, suggesting the main wiring harness might be ok. The issue developed gradually over about 2 weeks, starting with intermittent beeping from the obstacle detection system before failing completely. No car washes or unusual weather exposure during that time. Going to have the proximity sensors tested individually since it sounds like it could be an isolated sensor failure rather than the complete wiring issue you experienced. The gradual failure pattern makes me think its more likely a failing component than sudden water damage or wiring break. Thanks for sharing the repair cost reference. Will update once I get it properly diagnosed.

Thanks for those extra details about the gradual failure pattern, that does make your case sound quite different from my Smart Forfour experience. With your parking sensors failing progressively while the rearview camera keeps working, it points more toward a sensor-specific issue rather than the comprehensive wiring problem I dealt with. In my followup experience with blind spot sensors and parking aids, gradual deterioration often indicates failing sensor units themselves. The control module typically shows distinct error patterns when individual parking sensors start degrading versus complete wiring failures. Since your system worked fine until recently and theres no physical damage, you might want to have the workshop focus on testing the individual proximity sensors first. The diagnostic costs should be lower than my full rewiring job, though sensor replacements themselves run about 60-80€ per unit if needed. The fact that your rearview camera works perfectly is a good diagnostic clue, in my case the corrosion issues affected all rear electronic systems including the camera. Let us know what the techs find when they test those parking sensors individually.

Thanks for the input. After comparing the symptoms to other cases, I'm now pretty confident its sensor-related rather than a complete wiring overhaul like mentioned. Just booked it in for next week to have the ultrasonic sensors tested individually. The gradual failure of the parking assist system while other functions kept working does suggest individual component issues rather than widespread faulty wiring. Going to ask them to focus diagnostic efforts on the proximity sensors first since thats the most likely culprit based on the failure pattern. If it is just one or two bad parking sensors causing the fault codes, the repair should be straightforward and less costly than rewiring. Will share an update once I get the proper diagnosis on which sensors failed. Really helpful to hear about similar experiences, saved me worrying about more complex electrical problems in the parking assist module.