Will the rear passenger door of a 2002 Cadillac deville fit on 2001 deville?

While the 2001 and 2002 Cadillac DeVille are very similar, there's no guarantee that the rear passenger door will be a direct swap. There might be subtle differences in the door structure, wiring harnesses, or even the latch mechanisms between the model years.

It's best to check the part numbers of the doors. You can usually find these stamped on the door itself or in a parts catalog using the VIN of each car. If the part numbers match, it's more likely to be a direct fit, but even then, there's a small chance of minor incompatibility.

Without checking those part numbers, you can't be absolutely sure. Trying to fit it and discovering it doesn't work properly could cause more problems than it solves.