Huh! Well, that's an interesting question and I don't have a straightforward answer for you.
But I do have some thoughts:
The BE/BH Legacy is a MAP setup with a standalone IAT sensor in the plastic "grunt box" right ahead of (from the perspective of air going into the engine
) the throttle body. It should be easy to get a hold of that sensor ( AIR CLEANER & ELEMENT. AIR CLEANER '00MY-'03MY.. For 2001 Subaru Legacy 2.5L MT 4WD L Wagon | Subaru Parts Online
The next step is to figure out whether:
1) its connector is the same
2) its electrically compatible
3) and it has the same calibration
(1) isn't a deal breaker, just cut n splice as needed. (2) is pretty likely (same era and temp sensor tech doesn't change that often), but (3) is where you're going to run into pain if it's wrong.
So, the real trick is verifying that calibration. You have a couple options there:
- You can either research by part number, maybe try and find the OEM for the sensor and see if you can get a calibration from them.
- You can take a look at the manual for both cars and check the troubleshooting section for the temp sensor and see if you can work out the calibration based on that info
- Or, and this might be easiest: Pick up a sensor from a junkyard and just bench test it. Temp sensors work by changing resistance at different temperatures, so you should be able to test with a multimeter without even applying power. Grab your current one and the new one and test both in the fridge, at room temp and over your toaster
Uhm, if I misspoke anywhere, someone should let me know, but I think that's at least mostly accurate. If you do end up doing this I'll be super curious how much the difference is in temperature. Good luck!