* Check the owner's manual: If you have the original owner's manual, it will list the vehicle's options.
* Inspect the engine block: Look near the engine block, particularly around the freeze plugs, for a cord that would connect to an external power source. This is a telltale sign of a block heater. It's usually a fairly thick cord.
* Look at the electrical system: Check the owner's manual or the wiring diagrams to see if a block heater is listed.
* Check the vehicle's history report (if available): This might indicate if it was originally equipped with this option.
In short, it's not guaranteed, and you need to check the vehicle itself to be certain.