I got these codes yesterday and was wondering if anyone has any trouble shooting ideas to prevent auto shops and hopefully change what needs to be changed myself. I changed the rear O2 sensor about 2years ago. So not sure if the forward one would need to be changed. Any help would be greatly appreciated. This forum has always been a great help in the past. Thank you

How long ago did this occur and have you ran through a full tank of gas yet since it first lit up?

I actually downloaded it and erased the code and it has not come back. So do you think if something was really wrong the light would keep coming back right?

Yes, if something was wrong, they'd come back on.

Well it did come back yesterday. It said 2 codes but when i downloaded it there was only the P0171. I had the harder of the 2 O2 sensors replaced 2 years ago. Should I change the other one or what should i replace? Thanks for any help.

If not seized, the front A/F sensor is pretty easy to replace, you can go to Autozone for the loaner tool. Soak the sensor with PB Blaster and wrench it off.

Keep erasing the code for a bit, and see how often the code comes back on.

Thanks guys. I erased the code again and it takes about 30ish miles for the CEL to come back on. How hard is it to change AF sensor? Where can i get a AF sensor from cheaper then Lexus? Do you know of any DIY on this project. I was just wondering if this is the solution to this. Sorry for all the questions. Thanks all the help on this.

Cheapest A/F sensor I've seen is amazon.com for $127 plus shipping.

I just cleaned MAF sensor. found s thread a guy did it and it fixed it. But what should my next option be to do?