2000 Nissan Xterra Knock Sensor Testing

Thanks for linking in the video!
The back probed voltage check you did indicates that the sensor is not open like the one in the video. I'd check it disconnected also just to prove that voltage rises to near 5v ruling out a partial short (which seems unlikely in my opinion).

If the sensor was connected when you back probed it for resistance testing, then that test is invalid. If it was disconnected, you should be fine.

Also, what exactly is the code you're getting? (And the engine size if you don't mind so that we can get service info if it comes down to it.)

As Noah .... keep in mind because of engine vibration and movement intermittent faults are pretty common in engine mounted sensors and the wiring.

A tap test on the sensor using scope is really handy for this type of problem, without a scope you could try the tap test on the sensor and listening for a change in engine note at idle but on modern engines usually the IAC corrects the idle speed so quickly it is difficult to detect.

Without a scope you are really down to substitution testing (OK parts swapping) which for test purposes you could do without removing the old sensor, just connect the new sensor without screwing it in to the block. As long as the sensor isn't rattling about on a hard surface it shouldn't trigger a knock detection by the ECU.

Knock sensors are pretty simple things -- just a piezo-electric crystal not dis-similar to reversing sensor. Misfires or general rough running vibrations are outside the frequency range they can pick-up

Kinda a crappy job to get to the knock sensors on this engine, unfortunately. But, if you found 2.5V at the knock sensor wire and still get repeated knock sensor codes, then I think you're safe to replace. I've seen the sensors on this engine fail so they'll trip the code, but will pass resistance tests.

I say do eeeeeeeet. I'm cool with the 4.88V unplugged, nothing to sweat there. You can just live with the code if you want (as it won't trip the CEL), unless you live in a state that would consider that an emissions failure.

Yeah, just about every 3.3L I see has this code in it, and most drive around like that forever with no real issues. Those knock sensors aren't cheap, either.

Tempting to suggest substituting a resistor in the circuit in place of the sensor, unless the computer looks for activity on the signal it should work --- If you do this stick to using high octane fuel.

Oh you'd absolutely get a code, probably P0328. I've not looked at the code set criteria on this one for awhile, but I'm pretty sure it looks for signal wire activity.