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How to Fix a Stuck Gear on a Smart 451

Model: Smart Smart 451 - Years 2007-2015
Part: Transmission

In this video, we will see how to resolve the issue of a stuck gear on a Smart 451 (the famous three flashing dashes), where the vehicle remains stuck in neutral. The main cause is a plausibility error between the stop light switch and the brake pressure sensor. Reading the errors with the diagnostic tool, errors related to a flat battery are found, but the real issue is in the ABS. Through diagnostics, the values of the brake pressure sensor and the stop switch are checked; if pressing the brake causes the pressure sensor to rise but the stop switch does not signal "pressed", the ABS control unit does not give consent to engage the gears. The faulty switch is located under the engine bay, rear side. You will need to remove the lower protections and open the inspection door, and replace the faulty switch, then clear the residual errors with the diagnostic tool.

Posted on 31 March 2026 by ScegliAuto

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