Well it is not just possible but common practice to do relative compression tests on OBD2 engines with a laptop
Google: laptop compression test video
There are two tests, one is the cranking test, no fuel added, other is running test
The crank sensor and cam sensor can tell "you" how much the crank/cam slowdown when cranking, on each cylinders compression stroke, if it slows down less then lower compression in that cylinder
Running test is done by "power added" when cylinder fires, this is how computer IDs and sets misfire codes
But there is an extra step, the computer cuts injector signal, like a power balance test, and watch the relative speed that the crank/cam slows down which is compression resistance
We are used to gross analog seconds and minutes, the engine computer and sensors gets down in the milliseconds, so timing delays is easy for it to do
These are all based on "average number test" so its like a regular compression test, the actual number doesn't matter, well within reason
If you have an un-calibrated compression tester, it might show 130psi when actual number is 160psi
But if you test 6 cylinders and 4 are 125-135psi and 2 are 100psi then you know there is a problem in the 2 low ones, so the actual numbers are not relevant except to show 2 are different
But a compression test doesn't tell you WHY a cylinder may have low compression
Generally if its not blowing white smoke on start up(head gasket) then its a burnt exhaust valve
If you want another non-intrusive test you can do the burnt valve dollar bill test
Google: burnt valve dollar bill test
You can also use a lighter next to tail pipe to see if the flame is SUCKED IN to tail pipe when #4 comes around
In any case I would change the spark plug in #4, new one or just swap it with #5
And give it a good look, if its blackish then oil is getting in, valve guide seal