CEL VSC TRAC OFF?? 03" 4Runner

[azurez14]

I used an Actron code reader and it came up bad O2 sensor on passenger side downstream(past the catalytic converter). Replaced it with a new OEM Denso and cleared the code. 2 days later the same lights came back on. Rechecked with the code reader and the same trouble code came up even though the O2 sensor had been replaced. Anybody have any ideas as to this problem?