I have a 2019 ES350 with about 19k miles on it. About a week ago I got a check engine light for a lean condition on only bank 2. Upon checking the data with a tool I confirmed both banks were in the high 20's. I did some basic research and found that a dirty MAF may cause this issue so I cleaned it and reset all codes. Things were fine for a few days then the code returned, P0174 and P0171, this time it was for both banks. It also gave me codes P0455, P0441 (this is the only and only time I got these codes) and P0505. I re-did my gas cap and cleared the codes and again for a more few days it was fine. I noticed that Bank 2 consistently ran leaner even within normal ranges so I was thinking maybe a dirty injector. I bought and added someRedline S-1 before filling up and drove it on a 3 hour each way trip. I drove the car around town a small amount while there and then home without any issues or check engine lights. Once I got back home and was driving home from work I noticed a high idle on startup, checked the data with my tool and both banks were in the 30's again. Shortly after it tripped my check engine light again, P0174 and P0171. It also always triggers a Parking Support Brake Malfunction message at the same time the check engine light tripped but I didn't notice any issues. I noticed that when accelerating even moderately the LTFT's seem to improve dramatically but then when I left off the gas they returned to their elevated state. The next morning heading to work upon startup and the first 5 or so minutes of my drive LTFT's on both banks were still in the 30's but then it seemingly randomly started dropping to normal levels around 3 on one bank and 7 on the other. I know these aren't ideal but also are far better than what I'm getting when the issue occurs. The LTFT on both banks will be very lean normally around 38-39 for some period of time and then on it's own drop down to around 3 on bank 1 and 7 on bank 2. This ranges from driving just a few minutes down the road to maybe 20-30 minutes of driving. I live near my work so don't drive very far distances in general. It doesn't seem to me that the issue occurs when the engine is only cold or hot or on the first start of the day, seems to be fairly random but it's occurring more frequently than originally.

Today the issue occurred after making a shorter drive during the day and then starting the car back up about 30ish minutes later. There was a noticeably high idle so I checked the data with my tool and it was in the high 30's. During my drive to get lunch I noticed again that when accelerating both LTFTs improve dramatically to near normal levels then returned to high 30's under no load. I checked the codes and this in addition to my P0174 and P0171 codes I also had a P0505 for idle air control system.

I noticed for about 45 seconds I had a steering wheel warning light with an exclamation point on the bottom left of my dash during startup after lunch but then it disappeared and never returned. While driving back to work from lunch after about 6 minutes the LTFTs start improving on their own and settle out around 3 and 7 respectively. This didn't turn off either check engine light on my dash but the car responded better and didn't have a elevated idle. Luckily this time I had a scan tool hooked up recording all of the data during this period so I am able to review it all from my tool. I can clearly see when the LTFT's fix themselves but not sure what else I should be looking at during that same period. Unfortunately I don't believe my scan tool allows for the data to be exported but I am able to graph out 4 items together. I could take a video or check the data myself if anyone has suggestions on things to check.

I am out of my depth on this issue, given how it's intermittent and "fixes" itself I am not sure where to start looking. I am thinking about taking the car to a local Toyota dealer (Nearest Lexus dealer is 4 hours away) to see what their diagnoses is but honestly would rather fix it myself. I would greatly appreciate any input or suggestions. I am more than happy to check/post any data that would be helpful in diagnosing this issue or complete other testing etc. I am fairly mechanically inclined just not used to working on such a new car. Thank you for your time!

 

You may want to take a look at Technical Service Bulletin (TSB) L-SB-0005-23, February 9, 2023, Fuel Pump (Loss of Fuel Pressure) (pdf) with an introduction of:
(In case you don't know it, Malfunction Indicator Lamp (MIL) ON is AKA check engine light on.)

If repair cost is a concern, if your ES's problem is indeed the issue addressed by the TSB, the TSB states the repair is covered under the 72 months or 70,000 miles Lexus Powertrain Warranty.

 

Out of curiosity what is a “system too lean” condition?

 

For a general explanation, this Long Term Fuel Trim and Short Trim Fuel Trim article looks to cover the bases.

For Lexus ES specifics, you can search the lexusguide.net Lexus ES (XZ10) Service Manual on one of the P0171 or P0174 codes. Amongst the search results, digging through the information on the System Too Lean Bank 1 (P017100,P017200,P017400,P017500,P117000,P117B00) page will give you a good idea on what it means specific to the ES 350 engine and the means of monitoring and determining when a "too lean" code is set.

 

Thank you for your response! I believe that previously this pump may have been replaced, I am showing that 10/7/2020 it had service items "Replace Low-Pressure Fuel Pump". Do you by chance know if this the same pump being mentioned in this TSB? I noticed that this TSB is from fairly recently long after that work was completed so that may be something to look into still.

Yesterday after filling up my car with gas it wouldn't start. I waited about 10-15 minutes and it started up but was a very hard/rough choppy start followed by a high idle about 1500-2000 rpms. I let it idle for a few minutes and it fell to about 1000 rpms so shifted into drive and made my way to work. I moved the car once at work after about 1-2 hours and it started right up no issues at all but still had an elevated idle.

After doing some more research I have found a few other people with the 3.5 V6 that experienced very similar issues and data from a failing (intermittently it seems in my case) Vapor Canister Purge Valve / Solenoid. I am hoping that this may be my issue as well so I ordered the part and plan on replacing it as soon as it comes in. Thankfully this part is located in a very easy to access/swap location as well. I had all of the following codes in the system and will not be driving it again until I get it replaced to hopefully resolve my issues.

Codes: P0505, P0174, P0171, P117B

 

I am happy to report that replacing the Vapor Canister Purge Valve / Solenoid seems to have resolved my issues! My idle issues have disappeared and fuel trims have stayed within an acceptable range with no CEL's or codes in the system. I have done a mix of highway and city driving since as well. I hope this will help others in the future. It is a very simple part to replace, took under 10 minutes total and is right on top of the engine. Rock Auto had the best price for mine.

My part was: Vapor Canister Purge Valve / Solenoid STANDARD MOTOR PRODUCTS CP808 (https://www.rockauto.com/en/moreinfo...&pt=4936&jsn=1) OEM / Interchange Numbers: 258600P030, 258600P090, 2586025010, 2586031110, 2586036111, 2586037060, 25860F0010, 9091012283, 90910AC004, CP871, CP954, CP988, CP992, CP994

Please check to make sure you order the proper part for your make/model, I have a 2019 ES 350 UL.
Best of luck!

 

Has the issue popped up since replacing the Vapor Canister Purge Valve? I'm having this same issue. Lean on 1,2 intermittently. P01441 codes on and off. ITs been happening for some time now and my idle is a bit rough, although no issues when im accelerating. I'm thinking of replacing this part based on your comment before i take it to a mechanic!

 

Had a very similar issue with my Lexus . I had code 171,174 and 505. Checked for leaks with carburetor cleaner and couldn’t find a leak. After reading this thread I checked the purge valve and it was open and sucking fumes from the gas tank. I ordered a replacement part and while I waited I cleaned the purge valve with MAF cleaner and put it back in. So far no codes idle dropped to around 700 and runs a lot better. I will hold on to the replacement just in case but besides the codes my long term trim was in the high 30s and now it’s close to 2. Thanks for this forum it has definitely saved me from dealing with the dealer.

 

Thank you. Check engine light came on last August, along with brake warning, and a light that appeared to be a rear parking sensor with a light above rear of trunk on right side of dash. Same codes as well. Both banks being lean. Air Filter was past its life, changed the filter and new gas cap. All warning lights went off after 20 minute drive without resetting the codes. The same dash lights returned late March of this year as well as an evap leak code on top of both banks being lean. Definitely wasn't the air filter- replaced nonetheless along with another gas cap. No go. It would then have a hard time starting after each fuel up regardless if it was 5 gallons or full fill up. I recall this post from before and also read up that a purge valve test was something to look into before diving in deeper. Saw your post yesterday and bought some MAF cleaner on my drive home. Pulled the purge valve yesterday and sure enough it was open - I could blow through it from both ends. Sprayed it really well with the cleaner and let it dry for about 30 minutes - made sure no moisture or drops were left. Pulled the MAF sensor as well and gave it a good spray and let it dry. Reset the codes and all good. Went to top it off just to make sure and no hard starting. Thanks again. Dealer would have been a nightmare to diagnose and start to randomly change parts.
update - despite cleaning the purge valve and clearing the codes - the same codes popped up 50 miles later. I bought a new valve and installed it - the one I pulled off appeared to be working as it was not open like when I originally pulled it off - however it does appear to have a hairline crack in the grey part of the plastic. Installed the new one, cleared the codes and all looks good about 100 miles in. Btw - this is the purge valve that is close to the intake tube that goes from the air box to the throttle body and is partly visible with the engine cover on (driver side of engine cover) - not to be confused with the other one that is closer to the passenger side and out of view with engine cover on - that one actually looks more like a canister as it has a cylinder shape - I mention this because the Lexus parts guys will ask which one you need. Apparently the other one gets returned quite often, whereas the one I bought does not and did the trick.

 

2019 Lexus ES 350 123,000 miles. Im having the same issues. I first noticed that when at the filling station my gas cap was pressurized and whenever I removed the cap it was full of air. After filling the tank I would experience the engine spinning but would not start regardless of the level of gas I pumped. Finally after pressing the start button upon the 7th try it would stumble and start. I replaced the fuel cap from Toyota/Lexus. I Replaced the purge valve along with the short vacuum hose that was dry rotted leaving the purge valve going into the throttle body. When I was checking my old purge valve I tried blowing air through it and it wouldn’t let me blow air through it. But after replacing the purge valve I noticed that the fuel cap didn’t have pressure when unscrewing the cap. I had my codes cleared and drove 500 miles no lights. I guess we will see! If the light comes back on I’m going to clean my mass airflow sensor. About two oil changes ago the Lexus service advisor told me that my air filter was needing attention so I had it replaced. I guess we will see how it goes