Scanning is a method for the Transformers to change their alternate mode into the native things from other planets, such as vehicles or animals on Earth. A Transformer's scanning ability is enabled by their T-Cog component. However, by scanning a new alternate mode, their robot mode appearance doesn't change.

For some reason that has yet to be explained, Cybertronians seem to lose the ability to assume a vehicle form after arriving on Earth. While they are perfectly functional in robot mode, their inability to transform puts them at a disadvantage regarding mobility. Though there are some exceptions. However, Cybertronians are readily capable of scanning local vehicles for alternate modes. This appears as the Cybertronian in question shooting what appears to be green (or blue) beams from their eyes. The beams scan the vehicle, which appears to cause some electrical interference as well, providing the Cybertronian with a complete schematic of their chosen vehicle. After which, they can immediately transform into said vehicle. Curiously, Cybertronians appear to display kibble that already hints to an Earth vehicle mode before they actually scan one.

William Fowler has inadvertedly provided some Decepticons their vehicle modes with the vehicle he's currently riding in, much to his irritation. 

Optimus Prime scanned a new alternate mode that would better integrate his new jetpack. The vehicle chosen by Agent Fowler was a M.A.S.K. division experimental, all-terrain, expeditionary fighting vehicle.