I've been recently encountering an annoying p0171 & p0174 on my 2001 Lexus LS430 V8 4.3L, I hooked up a scanner after removing the battery overnight to see how the ST and LT fuel trims looks like. ST are constant at 19.47% (Surprisingly. Both banks are having the same exact number) While LT's are at 35.24 (Also both of them are the same number).

O2 sensor 1 Bank 1 & Bank 2 both are reading 0 Volts in idle, If I rev it a bit it can increase to 0.2-0.6v, and once the gas pedal is released, they will come back to 0 volts instantly.

So far, I have replaced the MAF sensor, Replaced Intake manifold gasket, Replaced Injectors(Mileage is far better now), and checked all the vacuum hoses for any holes or cracks. all good. I even sprayed WD40 all over the intake edges and hoses just to ensure if there is any vacuum leaks. and the RPM is steady at 720-740.

Now whenever I erase the codes they will never come back if I'm driving around (means higher rpm), Once I come to a stop or a parking, they will come back again instantly.

This is really annoying as I've paid too much trying to solve these annoying errors and nothing worked yet. Car drives OK, and accelerates just like it's supposed to do. Mileage is 17-23 MPGs depending on the traffic, which looks like normal. HOWEVER for some reason.. she still doesn't like the air-fuel mixture can anyone help me please?

 

https://www.clublexus.com/forums/rx-...174-codes.html
Looks like the same symptoms