Seems like this is an old thread, so I don't know if anyone will respond.
I have a 1999 4runner limited that I bought used (not at a dealer).
I'm having problems with the electrical connector that connects the brakes to a trailer's brake lights. I was told it might be a problem with my converter box. I think the converter box was factory installed, (drivers side in the rear, underneath inside panels). The converter box says 'Toyota' on it.
There is no electrical current going to the trailer hitch connector (verified with continuity tester), and fuses are good.
How can I tell if the converter box is 'dead' or if I have problem somewhere else? Someone above said a replacement from a dealer is like $200! Are there problems if I use a non-toyota dealer part? What are other people's experiences?

Thanks in advance for any help.

 

read my earlier response above