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Hey, I think you may have just saved me a ton of time and frustration chasing the same 2 codes. I moved the control valve when the engine was at idle and it smoothed out. I cleared the code and it hasn't returned. So we'll be watching this one and will replace the control valve if it returns. Thanks a million for posting this.
Hi did this ever fix your issue? Youre probably not going to see this but i am having the same isuue thanks.
Thank you for taking the time to detail this out. I too am in the same boat with limited time as Lexi the Lexus cannot pass emissions, we are literally on borrowed time. I have kicked every issue except these P0171 and P0174 codes. I hope this will be the final resolution. She is a great vehicle.
Thanks again. Lex_US_Fix_it
[QUOTE=HtownBlue;7684563]P0171 and P0174 I know this is long, but if you've had these codes, please read the entire post as it will explain EXACTLY what and why which will be important to tell the mechanice you work with.
If you want to know the solution, simply scroll down. What follows is an explanation of what I discovered. Let me start by telling you guys what I encountered. P0171 and P0174 are one set of codes that set off the Check Eng. and ECT and one other light on the dash I cannot recall at this exact moment...whatever.....engine detects these codes and sets off the lights.
Now what are these codes? Lean codes in bank 1 sensor 1 and bank 2 sensor 1. In layman's terms, the computer sees too much air in the system for the proper fuel air ratio and tells the injectors to stay open longer and add more fuel so as to balance out the ratio.
I pUT a for sale sticker on my LS430 year 2005 because of this P0174 issue as it turn off the Traction and I hated that!!
I did what you did changed and cleaned everything leak related now I'm gonna try this and hope.it works 😐 I don't really want to sell it been with me for 5 years now
Hiya mate I know it was 8 years ago nearly lol but I have the p0174 code on its own did you manage to find out what it was ? I've replaced maf and O2 sensors so far and they t keeps coming back
Thanks buddy
I had the P0171 and P0174 codes pop up after changing my sparkplugs along with the PCV and grommet. Knowing that it had to do with something I recently had done and since it was codes for both banks it was likely an issue prior to the cats/O2 sensors. I looked around and it ended up being old rubber tubing that had cracked at the ends due to age/miles and evidently was letting excess air in after being moved around when removing the PCV or plugs. I replaced theses sections with high temp hose and cleared the codes. They haven't come back since. Might be worth a check.
Last edited by jeepmoto; Jan 15, 2025 at 05:46 PM.
did you have LTFT 25%+ issues at idle or just with throttle?
I'm getting it with only throttle -- instant 25-26% + and then goes back down instantly almost to normal +-10% levels-- as if the ECU has learned this is what the car needs.
not to resurrect old thread but it would be really helpful thank you
I appreciate your diligence.
