hey, guys! my check engine light just came on and i'm wondering if it's for the same reason...i'm running a trd airfilter...i've actually had it in for quite some time, tho...i had a minor service done at lexus a couple months ago...i've been driving it for past couple days but no noticeable problems except gas mileage kinda worse...i'm gonna have my mechanic check it this weekend...hope it's something simple to fix

 

You would have to check the OBDII code with a scanner. Autozone has these as well as your Toyota or Lexus dealer. My Toyota dealer charges me here, because I am not a regular customer.

Anyway, what is probably happening is normal for the suspected causes.

1) You have a busted oxygen sensor somewhere (highly unlikely)
2) At some point something (particle) got past the filter, causing a light (possible)
3) You had a higher airflow at some point, causing a light (possible)
4) The MAF sensor is corroded. (possible)

Anyone of these, even if it only happened for a few seconds, will set off the light into an error.

1) Before you take it to get scanned, take a look at the MAF sensor just past the airbox, you need to remove the two screws, and look at the red diode. See if there is any gunk on it, use some brake dust or carburator cleaner. Then put it back in, pull the EFI fuse #13 for a few seconds, (10-30 will do it for sure). Then light should be reset.

2) For steps 3-4 also remove fuse as mentioned.

3) If light still comes back you could have a busted oxygen sensor, and then you would need to read the code, it will tell you in that case what sensor and what bank (location). Let me know once you get it scanned as I have an RX300 manual which lists the codes

Note, when you encounter this position, the car's air temperature for the engine air will go to something like 68F by default. This a safety feature so you do not overheat, which can happen if the MAF is corroded. More gas will enter the engine, and thus MPG will fall.