Toyota Repair: exhaust manifold cover/RX 300 2002, air fuel ratio, lexus rx 300

Question
QUESTION: Dear Mr Ritter          RE: 2002 Lexus RX 300
I've been noticing a loud noise that almost sounds like my muffler is going bad. while getting gas a man told me I should have my 'manifold exhaust cover' checked. If that is the problem what caused it to go bad? Could that also be why my check engine light and VSC lights are on again?  Last time you had me replace the sensor behind the engine that cost $300 & the lights went out.  Can you tell me what would cause the manifold exhaust cover to make a noise & the sensor lights come on?  What signs would my car be having if I let it go?  About what would the cost be?  once the exhaust cover would be fixed would the sensor lights go off or would they too need to be changed? Once again thank you for your knowledge & help,I really appreciate it!!!

ANSWER: Hello
At this time we don't know if the manifold is the problem but we do know the check engine light is on again so could you drive it to an autoparts store and have the diagnostic codes retrieved, they ususally do this at no charge and then we'll continue from there, thanks.

---------- FOLLOW-UP ----------

QUESTION: Hi Mr. Ritter, here is the info you requested: P1150 definition air/fuel ratio sensor circuit range/performance (Bank 2 sensor 1)

1)PROBABLE CAUSE: Fuel Pump, injector or pressure regulator fault, Vacuum leak on engine, Faulty AF sensor heater circuit, Failed AF sensor

2)P0174 system too lean bank 2 PROBABLE CAUSE: Lean air/fuel injector or vacuum leak, NAF sensor concern, ECT sensor fault, Faulty HO2S (heated oxygen sensor) Bank 2

3) C1201AGBS  OR C1710 he had no info regarding these codes.

I surely hope you can help me with this extra info so I can finally get the check engine light & VCS lights off and the NOISE & sometimes fuel odor gone.  I wonder what it could be doing to my engine. I just turned 93,000 miles on my RX300 year 2002.  THANK YOU ONCE AGAIN FOR YOUR INTELLIGENCE & HELP for single women!!

Answer
Thanks for the info, the definition of the 1155 code is correct, this is the sensor in the exhaust manifold near the front (radiator side) the code can also be caused by an exhaust leak at the threads of the sensor itself or a leaking exhaust manifold gasket, cracked manifold or another air leak before the sensor causing the sensor to read excessive oxygen content, since you are getting this exhaust noise this sounds very possible