P0504 after replacing brake switch, what to test next?

[jsjax]

Hey, long time reader, first time poster here.   Thanks for all the helpful advice so far!  Apologies if this is answered somewhere else, there seem to be a lot of similar cases, but I couldn't find exactly my situation.

I've got a '04 RX330 with the brake lights, VSC, tire pressure, etc...  on the dash.  I went ahead and replaced the brake light switch and the lights went away for about a day, and then they came back.  I then replaced it again with a different switch, and again, the lights went away for a day and came back.   (I tried both the bigger blue switch and the smaller white switch)

Both times, I pulled a P0504 code over OBD2 and I cleared it both times.  Both times that code came back.   

Other diagnostics:

• I tested both switches with my multimeter, they both seem fine
• I measured 12V, (well, 11.7V) across the plug when the key is in the ON position.   
• I've also tested all my fuses in the box underneath the steering wheel.  
• The car operates totally fine, it runs.
• The brake lights turn on as expected (all bulbs are working).

Does anyone have any ideas of what else it could be, or what I may need to replace?

Thanks in advance!

[RX400h]

Hello, James.

This is also recommended:

• Repairing or replacing wiring harness or connectors that leads to the brake switch or circuit

Sometimes vibration will cause a wire/connector electrical connection to be intermittent.

[jsjax]

Okay, that sounds like a good idea.

I assume that there is some ECU that is reading the switch position, and the fault could be inside that component.  Do you happen to know what/where that component is? 

[RX400h]

I do not at this time, but I'll see if I can find out where it is.