Just looking for some info on the GS540h particularly. Many of the threads I find pertain to other lexus models. Recently got a code for the MAF. My cars got 211,000 miles and I figured to just swap it out rather than try to clean it. Code went away but after a few weeks I got the P0174 code. Its my wife's car so I again questioned her regarding the gas she's putting in it. She replies regular...ugh...reminded her several times that she needs to put premium gas in this car. We bought it from a friend in 2021 and I've told her 5 or 6 times to put premium gas in it.

So here we are now, battling these lights and sensors. I've put Lucas complete fuel system cleaner in the car and ran almost a complete tank through the car. I've got a new gas cap on order. Are there any small troubleshooting ideas before trying to replace an 02 sensor? I've heard many troublesome things about the 02 sensors in 3GS models. Given the age of my car I'm banking on it being pretty stubborn.

Any advice is greatly appreciated. Also I've seen a lot of threads on here with very detailed diagnostics / info what source are you using?

Thanks!

 

Check this part 1226231050. It is a PCV hose that connects the passenger valve cover to the intake tube before the throttle body. Mine was cracked and was letting unmetered air into the intake causing code P0174 only.

 

Did you get this resolved? Check the master air flow in the engine or the oxygen sensor. easy fix. I had this same error before after I changed an air filter. I had not claimed the air filter box cover properly and too much air was getting in and causing it to be too lean.