sledguy24

im haveing issues with my rx being too lean on bank one and i was thinkin fuel filter cause it starts hard. its not my injectors so i was gonna replace my fuel filter before i realized i cant find it and cant get information on it could i get some help?

zombie

iTrader: (1)

bank one too lean is most likely your MAF sensor. either clean it or change it out with a new one.

Lexmex

Welcome to Club Lexus.

I wanted to confirm that what you have is a P0171 error. If this CEL (check engine light) has been coming on repeatedly then it could be just as Zombie said, the MAF sensor there is a thread at the top of the RX300 forum on gas mileage that has some instructions on this. If not and it just came up for the first time, you can check out same thread and it shows you how to clear it using the EFI fuse or pulling the negative battery cable, however of course and OBDII scanner can reset it, too.

However, I really want to confirm that you are getting a REPEATED P0171 as your error code and although usually it is something with the MAF or air intake, this is the complete list of trouble areas for P0171:

air intake (hose loose)
fuel line pressure
injector blockage
A/F sensor (the one behind the engine)
MAF sensor
engine coolant temperature sensor
gas leakage on exhaust system

sledguy24

i will confirm it is the po171 code i have replaced all my ox sensors except a/f sensor #2 (behid the motor) my first attempt is to clean the MAF and a fuel filter is not a bad idea as well does anyone know where the fuel filter is on the RX?

Lexmex

I don't really see need to change out the fuel filter on U.S. gasoline. I actually will be doing that before I go back to the U.S., but that is due to bad gas down here. I had it changed out once by Lexus a few years ago (when I already had a few years in Mexico and the gas was even worse back then) and it wasn't a pretty site.

However, fuel filter is located in area under the left side rear seat.

vinster29

I have had my check engine light come on four times in the past month and every time I get it checked out, the P0171 Error code keeps coming up with "system too lean, Bank 1 sensor 1." I had my local mechanic check my 02 sensors to make sure they weren't misfiring and he says that according to his readings, the front 02 sensors aren't working and the back 02 sensors are overcompensating for the front 02 sensors since they are not working properly. So my first question is: How many 02 sensors does the RX300 have? Should I just get my mechanic to clean my MAF sensor and just wait and see if the check engine light comes back or should I go ahead and replace both of the front 02 sensors? I would really appreciate any help on this one b/c I am not really sure what to do.

Fern

There are 3 o2 sensors one on each manifold and one after the cat converter.

Mine was burning too lean due to the one after the cat sending the wrong message and therefore causing the one on the "front" manifold to overcompensate and crack my manifold.

cost me a new manifold and labour and the rear sensor...

carguy07

Does the rear sensor actually think? On most cars the rear one is just a pass/fail emissions checker used to trip the CEL.

Lexmex

The one after the main cat below the vehicle is just used to measure the wavelength coming off the cat and emissions related.

The 2 A/F sensors off each manifold are the magic ones. What would be helpful is to see what resistance each A/F sensor has. I am kind of suprised as no other codes beside the P0171 error shows up and yes I would clean the MAF.