I have a 2002 xterra.I have a rattle under the dash.I have been a aircraft mechanic for 30 years,so I do have a little mechanical ability.I cannot find this rattle.It only rattles when the tires hit any type of small bump.It seems to be more noticeble when the steering wheel has a little pressure to the right.I have been addressing this noise for over a month.Its really got me.....

SOURCE: rattle steering wheel

Sounds like your intermediate steering shaft. Its the slip shaft that runs thru the firewall. They have a slip-stick condition that makes a horrible rattle that you can feel in the wheel. Its a pretty easy repair. Just make sure the steering wheel dosen't spin while you are changing it.

Good Luck

SOURCE: power steering noise

First thing is to check the level of the power steering fluid. If you're low, add enough to bring it back into range. If not, remove the cap and jack the front end off the ground (both wheels). With the cap off, turn the wheel lock to lock, back and forth, several times, to see if any air bubbles need to be bled out (this will bleed them). Then check the fluid level again and top it off as needed.

If neither of these helps, have the steering system checked by a shop - you may have a problem with the steering shaft, the tie rods, or the rack itself.

SOURCE: rattling in the dash

It sounds like there is a Dash Mounting Clip that has Broken and is Rattling against the Inside of the Dash. You will need to Remove the Front Panel of the Dash and check the Mounting Hardware for Breakage.

SOURCE: I have a rattle in the front end of my 02 maxima.

Sounds like sway bar links.

SOURCE: rattling noise in steering

Had same problem with new 04 Sierra, took multiple times to dealer. Final answer after 2-3 warranty replacements and repacks was that I should just live with it. The dealer suggested that I unbolt the steering column at the mid section (under the hood), and stroke the steering column back and forth. After getting over the fact that they wanted me to **** my truck off, to fix their crappy parts I gave it a try and it worked great. Needs to be done every few months. Don't mess with the bolts by the PS pump, just the single 15mm bolt halfway down. The back side is a bracket with welded nut on it so you just need 15mm socket. Paint match lines on both halfs. Pump the upper shaft back and forth after you slide it out from lower shaft. Takes about 5 minutes time.
The dealer said the grease gets hot and oozes down to bottom of tube so stroking redistributes it back up into the upper shaft.
Good luck