Other than OEM, what replacement bulb do I need for the low beam headlights? Also, if I put the wrong bulb(s) in for the low beam lights, would that keep the high beam bulbs from working?

 

My low beams are HID and I'd assume they come as a standard feature. If I'm right, there shouldn't be any "bulbs" to shop for and they certainly shouldn't be burned out, already.
Why are you looking for new low beam lights?

 

The RX's can have either halogen or HID. I believe the halogens are H11, but the HID's are D4S type bulbs.

 

OK, well it looks like IF you have halogen, the bulb would be H11. Since H11 bulbs are not dual filament, their replacement should have no effect on the high beam operation, at all.
The high beams appear to be a 9005 bulb.

 

On my FOG LIGHTS ON RX450h and LX570 I replaced with H11 LED bulbs bc OEM were halogen bulbs. The low beams were OEM HID's. So I left the low and high beams alone. I only changed out the fog light on these to H11 LED's.

But on my CT200H all were halogens. So I replaced both low beams and fog lights to LED's. I left the high beams alone.

Last month one of the led bulbs on my CT200H burned out. I emailed the vendor who sold me the led bulbs. The vendor replied back since they do not make the same identical exact led bulbs any more, they are willing to send me the new updated (and more lumen output ) LED bulbs to me at no charge. Since the new LED bulb will be brighter and not match the original one I bought from him. The vendor will just send me A PAIR for replacement. Excellent service! !!

The link is below:

https://www.amazon.com/dp/B01I3GKHQE

https://www.amazon.com/dp/B01I3GKHQE

 

The low beam bulbs burned out within two weeks of each other (after four years). I replaced them both, but now the outer headlights (high beam) won't come on. The inner low beam bulbs work but only when I activate the high beams via pushing forward on the headlight switch. The low beam function does not work. The outer high beams don't come on at all. I'm wondering if by putting in the wrong replacement bulbs, the low beam won't work and it somehow disables the outer high beam lights/bulbs from functioning.

 

OK, well that's kind of different from what you asked in the original post, don't you think!?! What did you replace them with?!?!!

 

The MOST OUTER lights are your low beams. The ONES MORE TOWARDS THE CENTER NEXT TO THE LOW BEAMS ARE THE HIGH BEAMS.

 

replaced them with inexpensive aftermarket bulbs from a local auto supply store. I had no idea what to use, they said the ones purchased should work.

 

There are better and cheaper ones out there. But if you like the ones at the local auto store, then that's fine.

Otherwise, please see my recent post (repeated below):

• 
  lexusrus , Yesterday 11:54 AM
  On my FOG LIGHTS ON RX450h and LX570 I replaced with H11 LED bulbs bc OEM were halogen bulbs. The low beams were OEM HID's. So I left the low and high beams alone. I only changed out the fog light on these to H11 LED's.
  
  But on my CT200H all were halogens. So I replaced both low beams and fog lights to LED's. I left the high beams alone.
  
  Last month one of the led bulbs on my CT200H burned out. I emailed the vendor who sold me the led bulbs. The vendor replied back since they do not make the same identical exact led bulbs any more, they are willing to send me the new updated (and more lumen output ) LED bulbs to me at no charge. Since the new LED bulb will be brighter and not match the original one I bought from him. The vendor will just send me A PAIR for replacement. Excellent service! !!
  
  The link is below:
  
  https://www.amazon.com/dp/B01I3GKHQE
  
  https://www.amazon.com/dp/B01I3GKHQE