duane

Very sorry to hear about your cat. Can you tell us what the part was replaced to fix the problem. It would help out the forum for any future similiar problems

Duane

MarkG2000

A week ago I had different error.....302...changed all plugs to NGK still got the error. Swapped the coils in 2 & 4 and code came up 304...hence the #2 coil was bad...bought new one $87 although I know online is $60s. Car running great...that was Friday...got on the freeway Sat! Engine light got my sensor out to get a NEW read...PO171.
Here's a rub. Not just 9 months ago I had BOTH O2 sensors changed so I wonder if one already went bad.
OR

Do one each of the other suggestions...fuel intake with tank of gas
and others. Don't know about cleaning MAF(where's that?)

comments

hypervish

MAF sensor is on the air filter box, look at the diy for cleaning it in the sicky tap called "diy's"

MarkG2000

Changed the Air Filter and had the car fully gassed since several days ago when reported that a new PO# came up after changing all plugs and the coil #2.
PO171

After reading some great posts on what to do....Got myself the CRC MAF Cleaner can. Sprayed several times on the sensor....but nothing happened.
Engine light continued to shine....UNTIL TODAY.

Filled the tank from near empty...Not more than 1/10 from station

LIGHT OFF.
Just checked this by turning car on/off 3 or 4 times...ALL GOOD.

. B
2000 yr rx 300....178k just OS sensors changed and plugs. Still haven't changed out the Airservo yet...broken for 3 yrs rattling stopped 2 yrs past...Live in CA so I still have A/C...just no heat
I want to thank all of you for the info posted here and saving a TON of $$...again thx

whc51457

My 1999 Lexus RX300 CEL light had come on. Went to Autozone and it was throwing a P0171 code. I replaced the MAF sensor and also check around for vacuum leaks. Reset the CEL and started diving the car. The light came back on but I continued to drive the car in case it needed to go through a couple of drive cycles. Now after 2 weeks of driving the car the light remains on. Not sure what would be the next best step to take. Any ideas or suggestions would be appreciated

salimshah

Please have the new code (could be the same), re-read.

Salim

whc51457

Same code after re-read. Thanks

salimshah

I dont know the right vacuum level, but have it checked.

Clean the sensor again, check air filter and make sure the small pipe is connected.

If that does bot work, then take it to a mechanic or replace the maf.

Salim

C-Stone

I have the same CEL with P0171 code on my '99 AWD with 140k miles (read by autozone). I cleaned the MAF sensor with electronics cleaner... which I've done in the past. (I have a K&N Air Filter). Resetting the code this time it came back during the next drive. Is it time to go after the A/F sensors? Bank 1, sensor 1 was replaced at about 60k. Bank 2, sensor 1 is original. I have both on order. But I'm going to do as Salim suggested in the the post above before I do anything.

Let us know how it turns out whc51457.

C-Stone

Any update on yours, whc51457?

Concerning mine... I cleaned the MAF sensor again thoroughly. Then drove it 2 days and the code came back. After reading this excellent article, I decided to replace my MAF sensor (original) since this code has been popping up more frequently.

So far many startups and drives, and no codes. Seems to drive nicely and gets better gas mileage. :-) I may not change out the O2 sensors now. The bank 1, sensor 2 is original.

artbuc

Here is a post I made a little while back re P0171 and barometric pressure. No one responded; but, based on what I have read and responses to similar posts on other forums, your car does not have a barometric pressure PID which can be read on an OBDII scanner.

https://www.clublexus.com/forums/rx-...-pressure.html

Having said that, I believe the RX must know (by direct measurement or calculation) barometric pressure because it uses it to determine if there is a leak in the EVAP system. Bottom line for me, I am totally lost when it comes to how the RX determines barometric pressure and if it can be used to diagnose MAF problems.

Edit: I just found this Toyota article which explains alot.

www.autoshop101.com/forms/h35.pdf

C-Stone

Thanks, artbuc!

nagpalk

Cleaning the MAF sensor dramatically changed my old cars shifting and acceleration!
When my check engine light came on, I thought it was the cheap gas (po171 code per the mechanic, who reset the light for me). But despite premium gas, the CEL came back again. In addition, I noticed the ECT power button mode was working terribly- lagging, hesitation, and jerking while shifting, sometimes no shifting unless I released the accelerator pedal. Thanks to the forum, I cleaned the MAF sensor using a $7 CRC cleaner, and voila! Night and day difference in shifting and acceleration, even on normal auto drive. The Check Engine Light gone as well. Love my car all over again!

Xtom73G

As the owner of a 2000 RX AWD, and 97 ES300 (wife's car) I have to say this; as cars become more computer intense and complex, many shops, "mechanics" and even stealerships, simply do not have the training, test know-how and also just like to start replacing parts and even whole assemblies, just guessing at what is wrong. Two small shop owners have told me that their business is just going to go away, because they can't afford to keep up with the changes, and as soon as they send one of their mecks to school, he quits and goes to a higher pay stealership. Sad.

Xtom73G

By the way, a note to think about; if you don't check your battery hold-down for snugness, and fail to keep those red plastic battery cable protectors over the terminals, you might experience what happened to a guy I know. He has an RX, and his girlfriend has the ES 300. On her car, the metal battery hold-down came loose, somehow contacted both battery posts, set the car on fire.