you will need a multimeter or test light, and wiring diagrams to diagnose the problem. Probe the switch, wiring harness, and motors to isolate the cause.

So is it mechanical or electrical?

It seems the wiring for the UP DOWN LEFT RIGHT control switch aren't the problem because they're working fine on the drivers side.

It seems the L/R Mirror Selector switch isn't the problem because you can control UP DOWN on the passenger side.

The mirror has 2 motors in it. One for UP DOWN the other for LEFT RIGHT.

The motors have worm gears on their shafts which mesh with round gears which move the mirror's mounting plate.

Let's look at it.

So all you need is your ear to figure out what's happening here.

Get an assistant. Turn the key to ON. (don't start the car)

Have your assistant operate the passenger LEFT/RIGHT mirror control as you put your ear against the mirror housing.

You'll hear one of three things.

1. Nothing (corrosion at the motor's electrical connection or motor burned out)

2. Motor Spinning but mirror not moving. (Plastic worm gear on motor shaft isn't spinning with the metal motor shaft)

3. Motor spinning but you hear Click Click Click ...... and mirror "jerks" but doesn't move. (one of the plastic "arms" on the plastic "nut" of the threaded adjuster arm (which engages into the slots in the hub of the above plastic round gear) that moves the mirror broke off

It's a repair you can do yourself (if you can find the parts) and you don't have to remove the assembly from the door.

But I'd look at prices for aftermarket mirrors for your RX 330 first.

Probably out there for around $80 and if you can't find these parts it will be easier to get

Why not just adjust the mirror by hand til it's where you want it and then leave it ?

The drivers side mirror on my 26 year old oldsmobile is the same way as your 16 year old and that's what I did.

Spend the money on a good dinner instead. :silly:  

Back before power outside mirrors. me and Fred Flintstone used our fingers. 😀 😀