Smart Fortwo Multiple System Failures & Control Issues

I faced nearly identical issues with my 2005 Smart Forfour. As someone with some experience working on cars, I initially tried using a scan tool to diagnose the problem when multiple warning lights started appearing on the dashboard. The check engine light would come on out of nowhere, and various electronic systems would fail intermittently. The radio would cut out, and sometimes the entire instrument cluster would go dark for a few seconds while driving. After attempting basic troubleshooting, I took it to a workshop where they diagnosed a faulty connection in the control unit wiring harness. The BUS system was not communicating properly with other modules due to corroded cable connections. The total repair cost was 155€, which included diagnostics and replacing the damaged wiring connections. The service required about 4 hours to complete, but it completely resolved all the unusual system failures and warning signals. The workshop explained that these issues are relatively common in vehicles of this age due to wire insulation degradation. What engine variant does your Fortwo have? Also, when did these issues first start appearing? This information would help determine if your problem has the same root cause.

Just had my 56761 KM service done last month, and it sounds exactly like what I experienced. The multiple system failures started appearing right after heavy rain. The control module issues were traced to water damage affecting the main wiring harness under the dashboard. A diagnostic scan revealed multiple error codes across different control units. The workshop found corrosion on several connectors leading to intermittent malfunction indicator activations and system failures. The check engine light would out of nowhere turn on and off during this whole ordeal. The repair involved cleaning all connectors and applying dielectric grease to prevent future issues. Total cost came to 220€ including parts and labor.

Thanks for the update on your Smart Fortwo repair. The water damage connection makes perfect sense with your symptoms, as I experienced similar issues after heavy rainfall with my Forfour. The way water seeps into the wiring harness creates those sporadic warning signals and system failures you described. The workshop solution of cleaning and sealing the connectors was exactly what fixed my issue too. Those unusual control module failures and warning lights are classic signs of moisture-related electrical problems. When water gets into the main harness, it wreaks havoc on the OBD-II communication between modules. The 220€ repair cost seems reasonable considering the work involved. For prevention, I would suggest checking the drainage channels and seals around the windshield and A-pillars. A blocked drain can cause water to pool and find its way into the electrical systems. After my repair, I have not experienced any more sporadic engine diagnostics errors or system shutdowns. The warning light issues completely resolved once the connections were properly sealed. Have you noticed any improvement in the audio system performance since the repair?

Thanks for following up on the electrical issues. After the repair work and sealing of the connections, all systems are working perfectly now. The audio system is back to normal and I have not seen any more unusual system failures or warning lights. The OBD-II scan shows no more error codes and the control module is communicating properly with all systems. The workshop did a great job finding and fixing the root cause. They also showed me where to check for blocked drainage points to prevent future water intrusion. The engine diagnostics are all clear now and I have driven through several rainstorms without any issues. The 220€ spent on the repair was definitely worth it considering how many electronic problems it resolved. No more unusual check engine lights or system failures to worry about. I will keep monitoring the drainage channels they pointed out to make sure water cannot get back into the wiring. Really appreciate all the helpful insights shared here about diagnosing and fixing these electrical gremlins.