It has been known for the throttle response on the smart to slow, or stop functioning, sometimes returning trouble codes P0120-P0124 (throttle position sensor).

You can either completely remove the top intercooler pipe for more access, or just undo the top connection into the throttlebody.

Pull the IC pipe out of the way.

Unplug the throttlebody connection.

Use an e10 socket to remove the 4 bolts shown.

The 2 at the bottom may be a bit fiddly.

Once all the bolts are removed the throttlebody will lift away, make sure you don't snag the seal when lifting it out.

As you lift the throttlebody clear, unclip the cable retainer on the underside of the unit.

The throttlebody will now lift out.

Here you can simply replace with a new one, refit as removal, or you can strip down and make sure all is okay.

Lever off the 6 metal retaining clips on the plastic housing using a thin watchmakers screwdriver.

Carefully open up the casing.

Check for signs of wear/penetration of oil etc, it should be oil-free in here.

Use some contact cleaner to just clean up the tracks on the back of the black casing, this will just remove any residue grease.

To remove the butterfly, use a T20 Torx bit to undo the 2 retaining screws.

Manually turn the servo motor to open the butterfly.

The butterfly will now just slide out the middle of the bar.

Clean up all the oil, make sure there are no marks, add in the black seal and refit.

Be mindful of the metal connections when refitting the plastic casing.

Clip the metal catches back on by firmly pressing into place.

Replace the green seal if necessary, ensure the little tab is poking out of the top of the seat in the inlet manifold, and bolt back into place.