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Smart 450 Gearbox Issue Resolved by Replacing Cables

Model: Smart Smart 450 - Years 1998-2007
Part: Transmission

This article addresses the classic problem of Smart 450 vehicles displaying three warning lights on the dashboard, an unmistakable sign of gearbox issues, which prevents the car from starting. The YouTuber replaced the gearbox actuator and then the clutch, but without significant results. With great patience, he checked all the electrical connectors and found some oxidised ones, specifically those controlling the gearbox from the ECU. By consulting the ECU error codes (using an OBD reader, an invaluable tool for DIY enthusiasts), he was able to read the error codes and discovered that there were broken and unsoldered wires that needed to be replaced.

Updated on 2 July 2026 by ScegliAuto

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