Lexus Repair: 01 Rx300 AWD, lexus dealership, maf sensor

Question
Hi, i recently went to my lexus dealership to get a diagnosis on a check engine light. i got 3 error codes 330,171, & 174.  THey said to replace the MAF sensor, which i did and i also replaces one of the two oxogen sensors in front of manifold. check engine light is still on. They said to start off with the knock sensors($280 a piece) but they tested good  when i gave the car to get a diagnosis. do you know what might be the problem?
thank you!

Answer
Hello, Well the first thing that needs to be done is to check the code numbers again to see what has changed if anything.MAF sensor is a common problem with the 171, 174 codes. If the vehicle is running lean this can creat a lean knock that can trip the knock sensors. I would focus on the lean condition first. In most cases if a O2 sensor is bad it will have a O2 sensor code also. So have the engine codes checked again to see where you are at.