Smart Forfour Door Lock Failure: All Doors Affected

Had a similar electrical issue on a Smart ForTwo 2016. The automatic locks failed completely on all doors. After diagnostic tests, it turned out the door sensor wiring harness had worn through near the driver door hinge, a fairly common problem on these models. The car alarm would out of nowhere activate due to faulty signals from the damaged wiring. The fix required replacing the entire door wiring harness assembly since individual wire repair wasnt reliable long-term. This was a serious repair that took several hours of labor since the door panels needed removal to access all components. Based on your symptoms, it sounds very similar to what I experienced. The high mileage and age match the typical timeline for this failure. Would recommend having the door sensor connections and wiring harness checked first, particularly around flex points near the hinges. The vehicle doors may need partial disassembly to properly diagnose the exact failure point. The complete loss of all automatic locks typically indicates a system-wide issue rather than just a single door switch problem. Getting it diagnosed properly the first time will save headaches later.

Thanks for sharing your ForTwo experience, really useful info. Im going through something similar right now with my Forfour. The contact signal seems completely dead and the door latch mechanism isnt responding at all. Wondering how the repair has held up for you since then? And if you remember what the total cost was for fixing the electrical issue? Planning to take mine in next week but trying to budget for the worst case if it needs a full harness replacement. Also noticed any other electrical problems pop up after the repair? Sometimes these door sensor issues can cascade into other systems from what Ive read in the forums.

The repair has worked perfectly since getting it fixed at the shop. The faulty door contact signal was resolved by finding a damaged connection in the wiring, much simpler than initially feared. The mechanic discovered it was just a loose plug connection near the door latch mechanism, not a complete wiring harness failure. Total cost came to 95€ for fixing the electrical issue, which included testing and securing the cable connections. Significantly less expensive than replacing the entire door wiring harness that I was initially worried about. No additional electrical problems have appeared in the vehicle doors or other systems since the repair. The automatic locks work smoothly now, and the door switch signals are reading correctly. Would definitely recommend getting it checked soon, these kinds of issues are often simpler to fix when caught early before they can affect other components. The key was finding a mechanic who properly diagnosed the specific connection problem rather than jumping straight to replacing the whole wiring assembly. Sometimes the fix for these electrical issues can be straightforward once properly identified.

After getting such helpful advice here, I wanted to update everyone on how things turned out. Took my Forfour to a new mechanic who actually specializes in electrical issues. Really glad I did some research first. Turns out the door sensor wiring was partially damaged, but not as badly as I feared. The contact signal was interrupted due to a loose connection block that had worked its way free over time. The car alarm would occasionally trigger because of this faulty connection. The mechanic found the issue within an hour using proper diagnostic equipment. Total repair cost was 120€ including labor, way less than I had budgeted for. No need for a complete wiring harness replacement after all. All electrical functions are now working perfectly. Doors lock and unlock smoothly, and no more unusual car alarm triggers. Sometimes getting a second opinion and doing some homework really pays off when dealing with car sensor problems.