On my son's 2006 Lexus GS 300 the check engine and VSC light were on. I ran a Techstream code test, there were many codes, one for the O2 sensor. It was not clear which one. My first action was to remove each of the 4 O2 sensors (no small task) and test heater resistance. All checked out ok. I put them all back, cleared the codes and the lights went out, no surprise here. Ten minutes of running time the lights were back on. I ran another Techstream code test and received a bank 2 downstream O2 sensor code. Not sure why this did not show up the first time. Replaced the O2 sensor, removed the codes, car runs great, no lights after 300 miles.