A car's PDI is its pre-delivery inspection, a process in which it is carefully looked over to check for any problems before it is sold. This is usually done at the dealership from which the car was purchased and before the vehicle is registered under the new owner's name. There are a number of different issues that a pre-delivery inspection can identify before a vehicle's sale is finalized.
According to Team-BHP.com, after a newly purchased vehicle has been registered under its new owner's name, there is little the owner can do if they find out it is dysfunctional in some way. For this reason, many owners choose to thoroughly inspect the vehicle prior to finalizing their purchase. Even if the potential buyer has already test driven the vehicle, it may have been damaged before the registration.
When performing a pre-delivery inspection, most people perform a cursory check of the car's exterior to ensure there is no new structural damage. They also make sure that all of the electronics in the vehicle are still working, and that the tires have sufficient pressure. Other small details, such as windshield wipers and floor matting, should all be present and functional. It is also important to verify that the documentation and sales contract are correct. Although this does not pertain to the vehicle itself, many people consider a final look-over of the documents a part of the pre-delivery inspection.