My X recently started knocking continuously. It does it when it is cold or hot and at idle and under loads. The check engine code showed up as 0304, which I believe means that the knock sensor or the wiring is bad. I took it to the dealer and they said replacing the knock sensor wouldn't fix the problem and wanted to charge me 1300 to tear apart the engine and try to find the problem. YEAH RIGHT! I brought the X home and I am wondering what to do. Should I just have the knock sensor changed or is there something else I should look at?

First rule of fixing/troubleshooting stuff on your own (for me anyway): Start with the cheapest/easiest potential fixes.

I don't know what a knock sensor sells for, but it's a good start.

EDIT: I guess it's a good start, but if the purpose of the sensor is to detect a knock, it seems like your ears have already "sensed it". So in summary, I have no idea what the hell I'm talking about.

I'm sure more knowledgeable folks will chime in though.

Best of luck.

magnus,
As johnnyx mentions, always start with the cheap and easy stuff. In this case, I'd pull the knock sensor ( wherever that is) and test it on an ohmmeter. If it's within spec, I'd start looking elsewhere...wiring etc.
Now, when you say knocking, do you mean something more along the lines of pinging, aka predetonation?. Have you done anything else to the truck recently? Tune up? Something else that could throw the timing off?
Bogatyr

Am I incorrect in thinking that the knock sensor doesen't cause knock, it just detects it, which allows the engine to try to reduce it? The engine is normally designed to run in a range that should not knock, the sensor just detects out of normal conditions, and does not affect normal operations?

So, if it is knocking without being under load, youve got a real internal problem (or timing issue), not a bad sensor. If that's the case, any further driving could really be hurting the engine.

You might be able to get some insight into the valvetrain or internals by watching a vacuum gauge and seeing how it behaves... (use a chiltons/haynes guide to diagnose with vacuum readings.)

PS - 304 is an engine misfire code, indicating cylinder #4 is misfiring more than 10% of the time. P300 is random misfire, then p301-312 indicate specific cylinder misfires (yes, the x only has 6 cylinders so it would never read 307-312, but it's a standardized error code). I would trust the PCM on this one, and focus on cylinder #4 for issues. Vacuum tests, compression tests, ignition tests, etc.

Yes P0304 is for #4 misfire. But that code is for a diagnostic scan tool. I checked the service engine light code which is for the knock sensor.

Should I try adjusting the timing and see if that stops the knocking or predetonation? If it does it would mean that the knock sensor is making the computer screw up the timing wouldn't it?

Since the PCM only retards timing based on knock sensor input, I would have a hard time seeing the knock sensor cause knocking... although if it's way retarded I guess it could behave badly regardless (would it even run??), or if the engine is already knocking and it isn't sending a signal to the PCM, the pcm won't try to compensate (I guess this does not matter, since the engine should NOT rely on the knock sensor to prevent knock under normal circumstances).

I would check the timing to see if it's within specs... I don't have a 2000 guide available, but the thread on service manuals should get you to that info...

For a 2K it should be at 15.

Vacuum guages are cheap. See if you have a loss of compression of difference from the other cylinders. Gas? Try filling up and see if it was a problem with that. Is there any loss of power/mileage? Smoke? Rise in Temp? etc...
Pay for an hour labor or so to have the problem properly diagnosed (this shouldn't require the engine being broken down, they can get close without doing this.) Just some ideas.