I have an 2004 L300 sedan V-6,it has the following codes P0174,P0171,P0421,P0431 the repair place is saying that all 4 O2 sensors and
2 cat converters have to be changed which does not track with me because P0174 says the engine is running lean!!! Is there anyone that might have some insight,need help

 

WOW! That's a lot of stuff to go bad all at once.

Personally, I'd go another way (just cuz I'm cheap). I'd locate the Engine Coolant Temperature Sensor (ECTS), and disconnect the plug (careful, its plastic), and measure the resistance across the sensor pins. If the measurement is above 5,000 ohms, or below 50 ohms, I'd replace the sensor - clear the computer, and do a couple of drive cycles to see if your error codes return. Part is about $15usd. Make sure to use teflon tape on the threads ...

 

Don't forget to write down the codes BEFORE you clear them.

 

i know you're trying to be helpful, but the codes are posted above

 

oh yeah duh ! not my best thought was it