Check Engine and VSC and VSC off lights are on. on 2001 Toyota Avalon

The 3 lights came on and I brought the car to the dealer who replaced one of the 4 O2 sensors. 9 days later, they came back on again. There were two factors that were present each time it occurred. My gas tank was about 1/8 full and I filled the tank. Next day, the car had been sitting in the sun and the outside temperature gauge read over 100 degrees (temp was actually about 80). Within 10 minutes of the temp reading and driving off, the idiot lights came on. I don't think it is the O2 sensor - please give me your thoughts?

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1 answer 1 comment
none of this is relevant without having the engine codes.
some parts stores will give you the codes for free. most
shops will charge a diagnostic fee.
although I cannot recall the exact code (0174 might be the one) it was a code for "lean mixture". Thinking out of the box, if O2 sensors are eliminated from potential problems, what would be the next logical system? Electrical? fuel filter? fuel injectors?