Good Day Lexus community,
i have a 2002 is300 sportcross with 223k miles. Over the past 3 years i have been fighting with a number of codes and working my way down and now i have been completely stumped. i bought a new car so i dont have to deal with the issues anymore but i still want to get her fixed up. I've had the car for 8 years and aside from the CEL i still love the car.

The first few issues i had were evap and catalyst efficiency below threshold so i changed the cats and the fuel tank check valve and cleared those codes.

NOW FOR THE FUN STUFF!!
P0156 showing b2s2 heated sensor malfunction has been pending and i changed both bank 2 o2 sensors with the same code pending
I got it down to 2 codes the p0156 pending and P0174 so i smoked the car and found that the o-ring for the elbow on the manifold that goes to the PCV was leaking so i changed the o-ring and its not leaking
Somehow that caused the P0171 to come on along with the P0174
The P0171 and P0174 codes i have tried going through the forms for months on it and most people fixed their codes with a MAF or changing vacuum hoses.
ive cleaned my MAF to no avail and then replaced it to no difference
Ive changed every hose that i can find with the throttle body off so i can see underneath. the only hoses i didnt change was the small ones going to the actuator for the intake baffle
ive cleaned the throttle body and air intake along with putting seafoam through the tank every month to try to clean the fuel system
I also changed my valve cover gaskets and cleaned my plugs because they were drowning in oil thinking that was causing less spark and i changed the fuel filter and strainer thinking it just wasnt getting proper fuel. i also changed the throttle body and upper intakemanifold gaskets
i get a loss of power between 2-4k only on highways though
im at a loss here. HELPP

for anyone that doesnt want to read all of that ill just list the parts that i have changed:
MAF
plugs about 8k miles ago
both bank 2 o2 sensors
valve cover gasket
fuel filter and strainer
air filter
vacuum hoses
throttle body gasket
upper intake manifold gasket
might be forgetting a few small things

 

The 171 & 174 are a vacuum leak. It will cause the other. I would get the car up to temp and spray carb cleaner on all the hoses and gaskets. If the rpm changes it is near the problem.

 

I've done that a few times with carb cleaner and starting fluid and i have not noticed any change.
im starting to think it might be the vacuum switching valve by the intake manifold or maybe the intake butterfly not closing at highway speeds causing too much air and making it lean but i havent seen anyone else with that causing a lean code.

 

also i dont know much about fuel trims but i know that mine are very off from normal. STFT is 1.6 and LTFT is 41.4
i hope theres someone on here that has a better understanding of fuel trims that can make sense of this. before i changed the fuel filter and valve cover gasket on the car the fuel trim was STFT -2 and LTFT 28 (still lean)

 

Do you think some injectors might not be spraying well? Or weak fuel pressure.

 

I was kind of thinking that, thats why i changed the fuel filter but i was too cheap to change the pump. I know these pumps go for a long time but i guess 18 years and 224k might be pushing my luck. i guess ill try changing that and finding a way to check the injectors flow rate

 

update: i got the car to pass inspection. The lean codes were caused by the fuel pump going bad.
Im now getting 2 pending codes for P0446 code for evap and i forgot the other code # but its cat below efficiency bank 2.
oh well, bought myself another year.

 

Cat codes, replace cats or put a simulator in and header.
The p0446 Is the charcoal conister. Needs to be replaced or one of the line is broke at it.

 

Would someone be familiar with the following error codes (2008 IS350);
- B1421 Solar sensor circuit Passenger
- B1424 Solar sensor circuit Driver
- B2281 P Signal (Cable-Information does not match to BEAN-Information / History
Any additional information is appreciated.

 

Wrong section. Try the right generation.

 

Thank you for the follow up and making me aware I navigated to the incorrect generation forum (IS model 2001-2005), instead of 2nd generation. I appreciate it.
Would you have any additional information / experience with the previous posted codes that may be useful? Again, thank you for your time.

 

So ive actually replaced the headers about 15k ago because i was getting cat codes then, i wonder if the car running lean for about a year and a half may have something to do with the codes im getting now.
after resetting the light im getting P0156 with P0420 pending and P0446 pending.
Ive read on the forum that P0446 is often the vacuum valve next to the charcoal canister that is a pain in the *** to change, any experience with that?

 

Yeah, it is a pain to change. If you go to do it. Replace the whole charcoal can with a new one not used.