If a part scanner is hovering over an already-placed engine part (see image example) text should pop up similar to the blue boxes that shows information you could normally see while an engine is in your inventory, as well as other info.
Things like engine hours, current engine RPM and temperature, oil/fuel/starter leaks, etc.

So, I've thought about this. and while I do see the benifit from a realizm standpoint, I also see the fact you're going to get a dedicated tool out instead of just hitting the engine with a wrench and looking at the tooltip. Additionally, instruments can show the temp, hours, RPM, etc, so really you can just look at them rather than the OBD. Or if you're cheap you pull the engine. Adding code to have the scanner look at parts and part slots would be difficult, and I don't see the benefit outweighing the cost of coding. As such, this will be a wontdo.

hot

Proof of Concept image

Total FC power as in how much power the engine actually has based on the fuel per tick variable, because it lets you see how much kick your engine still has or something I guess. Not required, just thought it'd look nice and add to the image.

Well that was stupid of me, now having seen some engine code

My only concern here is the huge amount of part boxes on vehicles nowadays that will likely obstruct the engine bay. For starters, collision boxes. If I'm over-worrying about this, let me know.

I mean, it's not like you can insert a plug into the ECU through a solid quarter-panel, or all tangled through the radiator. And for those vehicles, getting the engine in/out is probably already difficult anyways, meaning it's just a crappy car/plane/etc

In theory an engine variable could also be made that defines whether a part scanner can output info about it (for simpler/older engines) although it'd oughta be readable by default (probably not a good idea to add a variable for it though, would be too complicated imo)

May be a duplicate of #415

Not really. That one was more for tire wear, which I didn't want to (and still don't want to) get into. Using the scanner for engines might work with some coding changes. I'll put it on the table.

Tire wear sounds interesting, but too annoying to work on and use in-game imo.
Also, as I (think I might've? idk, may be wrong) stated in an earlier comment, it doesn't necessarily have to follow the example image via ordering or the weird engine power, I just thought it'd help illustrate my idea