Well if you read my other post about a 3500 rpm idle, (Topic here) you know the history. I got a used throttle body and swapped them out. Now I am getting a code of P0505. I never got this code before. So I took the original IAC valve off and put it on the replacement TB, but I still get the same code and it idles low/ rough. Any idea why it would just start giving this code when it never did before?

 

I would take it apart and I clean Every hole In the throttle body and check ur vacuum lines

 

yeah, i'm going to do that. It just doesn't make sense to get the code when it never did before.

 

Can a bad TPS cause this? If so, I might swap out the original TPS as well...

 

It might be the tossed. But ill tell u Toyota engines are run so much on vacuum . I have alot prob with vacuum on my truck as well right now.