Smart Cars are part of the Mercedes family, and accessing the On-Board Diagnostic system depends on where the vehicle was purchased. Smart Cars bought in the United States will likely use OBD-II trouble codes. Smart Cars bought in Germany and Europe will be using the European version of OBD coding. Some diagnostic scanners are able to read both sets of code, and you should make certain of this before purchasing a scanner. Retrieving the codes is a relatively simple process.
Place the key into the Smart Car's ignition. Leave the engine and electrical system off. Place your scanner's manual on the passenger seat. You will return to the key and the manual a few steps from now.
Locate the Smart Car's diagnostic outlet. This data link connection is covered and not in plain sight. Still, you will find it beneath the Smart Car's dashboard and to the right of the steering wheel.
Plug the scanner's cable into the outlet.
Turn the key in the ignition and start the Smart's engine. Scanners vary by brand. The button orientation is different, and so are the operational procedures. Some scanners only require the electrical system to be "on," while others need the engine running. Also, some scanners will self-activate, while others may need the "On" button pressed. Consult your manual for exact instructions.
Consult your manual for code descriptions and definitions. Your manual will likely only have the generic diagnostic trouble codes universal to all vehicles. Vehicles related to Mercedes have their own specific supplemental codes. These codes are available online (see Resource section).
It is easier to find manufacturer OBD-II codes by searching for "Mercedes" instead of "Smart Car."