Smart Roadster Cruise Control Failure Fix & Causes

I dealt with a very similar cruise control problem on my 2005 Smart Roadster Coupe. With some experience working on cars, this particular issue caught me off guard at first. The cruise control suddenly stopped engaging, and the dashboard light would not even come on when pressing the button. After investigating, it turned out to be a faulty pedal switch connection that was causing the system to malfunction. The throttle position sensor was reading incorrectly due to a loose cable connection. My workshop found that one of the main connectors had corroded, causing intermittent contact. They cleaned the connection points and replaced the damaged wiring section. The total repair cost was 95€, which included diagnostic time and parts. This is a relatively common issue on these models, often mistaken for more serious throttle position sensor failures. Before you head to the shop, could you share: Does your brake light work normally? When you press the cruise control button, do you hear any clicking sound? Has the check engine light appeared on your dashboard? Knowing these details would help determine if you are facing the same electrical connection problem I experienced or if it might be something different.

Thanks for the thorough reply. My mileage is currently at 141639 KM since the last oil change in June. Yes, the brake light works perfectly fine. There is no clicking sound when pressing the cruise control button, and no check engine or other dashboard lights are illuminated. I checked the fuse box and all fuses related to cruise control seem intact. I might try cleaning the connectors first based on your experience. If the issue persists, I will need to get the speed sensor tested since the complete lack of response from the system points to a possible sensor failure rather than just a loose connection. Would you happen to know if the connector locations are easily accessible without removing too many panels? Also wondering if using contact cleaner on the connections is safe for these systems.

Thanks for those additional details about your Smart Roadster issue. Since you mentioned being able to access the fuse box, let me add some specific insights based on my experience with the same problem. The connector locations on these models are a bit tricky to reach. The main cruise control wiring runs through the steering column, and some connections are located behind the steering wheel near the clock spring assembly. You will need to remove the lower dash panel for proper access. Contact cleaner is safe to use, but be careful around the clock spring area. Make sure to use an electrical contact cleaner specifically made for automotive use. Based on what you described, no clicking sound and no dashboard light activation, this actually sounds more serious than my initial connector issue. Given there is no response at all from the cruise control button, I would now lean towards checking: 1. The clock spring (these commonly fail around 140000 KM) 2. The steering wheel mounted cruise control switch 3. The main control module connections The complete silence when pressing the button is different from my case, where I at least got intermittent response. My throttle position sensor issue caused erratic behavior, but the system still showed signs of life. A professional diagnostic scan would be worth the investment at this point, as it will likely save time hunting for the exact failure point.

Based on all the helpful information provided, I will try cleaning the connectors first and will pick up some automotive-grade contact cleaner tomorrow. The symptoms do sound more severe than your case, especially with zero response from the system. The mileage definitely supports the possibility of a clock spring failure. Since my mechanical skills are limited to basic maintenance, I will schedule a diagnostic scan if the cleaning does not resolve the issue. A failed speed sensor or clock spring is beyond my comfort level for DIY repairs. The fuse box check was easy, but accessing those steering column connections sounds more challenging than expected. Rather than risk damaging anything near the clock spring, it makes sense to let a professional handle it if the initial cleaning does not work. Do you recommend any specific brand of contact cleaner that works well on these electrical systems? Also, roughly how much should I expect to pay for a proper diagnostic scan of the cruise control system?