Do it yourself
Frequently asked questions about cars and motorcycles
Car tutorial (Do it yourself) Motorcycle tutorial (Do it yourself) Frequently Asked Questions

How to Fix a Stuck Gear on a Smart 451

Model: Smart Smart 451 - Years: 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015
Part: Transmission

See other generations:
Video tutorial

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


Related tutorials

How to Reset the Tyre Pressure Warning Light on Smart 451
How to Reset the Tyre Pressure Warning Light on Smart 451
Smart (2007-2015 / 451) It is important to note that until the tyres of the Smart 451 are inflated to the correct pressure, the warning light on the dashboard will not turn …
How to Reset the Gearbox on a Smart 451?
How to Reset the Gearbox on a Smart 451?
Smart (2007-2015 / 451) When the letter N flashes on the display of the Smart 451's instrument panel, it means there is a fault with the gearbox. To temporarily resolve this…
Instructions for Removing the Clutch on Smart Fortwo 451 1.0 MHD
Instructions for Removing the Clutch on Smart Fortwo 451 1.0 MHD
Smart (2007-2015 / 451) In today's tutorial video, you will see the main steps to remove and replace the clutch on a Smart Fortwo 451 1.0 MHD. To access the clutch, first re…

Other guides you may be interested in

How to Set the Time in an Audi A4?

In this tutorial, you will see how to set the time in an Audi A4, a very simple and quick operation to perform after replacing the battery or when the time changes. First, insert the key and turn on the instrument cluster. Then, press the "SETUP" button located on the center console. Next, press the upper left arrow button, navigate to the "Time" option, and use the central knob to adjust the clock. Finally, set any necessary formats and save by returning to the main screen.

Watch the video!


by ScegliAuto

More videos