P0134 Error Code Keeps Appearing on '99 Toyota Solara

Hello -

Could someone please help me out?!? I have a '99 Toyota Solara and the check engine light came on about two months ago. When the OBD-II system was checked, the following error code appeared: P0134. I had the first oxygen sensor replaced, but the check engine light came on again. I forget what code came up the second time, but I was told it was for the third oxygen sensor behind the cat, so I had that one replaced as well. The code was cleared and I drove the car, but after about 35 miles, the check engine light came on again. I had the codes run and the P0134 code came up even though that oxygen sensor was just replaced. The wiring harness appears to be in good condition, so does anyone have any idea what is going on?

I have heard that the OBD must perform three consecutive tests on the system before the light will turn off, so could it be that I need to drive the car more and the light will turn off?

Please help!!!!!

Where were the sensors purchased? what brand were they?