RayN

2007 GS350 AWD, 120K miles, 2nd owner since 65K

@110K P0606, P0420 - fix replaced passenger side before cat O2 sensor (Denso 234-4521), used Actron CP9175 scanner to troubleshoot
@ 113K P0606, P0430 - fix replaced passenger side after cat O2 sensor (Denso 234-9058), used Actron CP9175 scanner to troubleshoot
@118K P0606 - fix replaced driver side after cat O2 sensor (NTK 24566, didn't used Denso coz it will take a week to get delivered), used Actron CP9175 scanner (didn't give enough info) and Techstream (shows the malfunction O2 sensor) to troubleshoot

I will replace the driver side before cat O2 sensor soon and will not wait for the OBD2 code.

ibidu1

iTrader: (1)

Do you have any exhaust leaks on your mid pipe? Do you still have the metal tin surround on them? A lot of times when you have exhaust leaks it will throw up o2 sensor codes or as a bad cat. Put the car on a lift while running, inspect the whole mid pipe area, remove both sides of the metal tin. You might need to cut them off as they usually rust. Theres a fiberglass matting under that tin that surrounds the exhaust tubes and after time that fiber gets wet and traps water slowly rotting your mid pipes. If your mid pipes are leaking you can take them to any exhaust shop either have them weld the leaks, or if its to badly rusted cut and install a new section of tube.

RayN

I have a modified Invidia mid-pipe to fit on AWD that was installed before 100K. I don't have any exhaust leak. Reset the check engine light multiple times and exhaust leak test using a smoke before I replaced the O2 sensors.

ibidu1

iTrader: (1)

Maybe the design of the invidia mid pipe o2 sensor bungs are not like oem so its giving you a super sensitive on the o2 sensor reading. Our o2 sensors are not prone to going bad at that early of a mileage. Check the position of the old mid pipe o2 sensors and the ones on the invidia maybe they are mounted more flush into the pipe. You might be able to get away with using o2 sensor extenders/ also called o2 sensor foilers if that is the case. All they do is extend out the sensor so it.

Just doesnt make sense how it killed some many sensors one after another. You might have another issue, with unburnt fuel. When was the last time you replaced your spark plugs? Ever do a throttle body cleaning/top engine combustion cleaning?

RayN

I did put back the stock exhaust (no leak) and did use the spark plug fouler O2 sensor trick, and that didn't work at all. Spark plug was replaced at 100K, throttle body and maf sensor cleaned once a year. PCV valve replace every other year. Oil - Mobil1. Use only brand name gas station. All recalls had been done. I have a log on all the maintenance and work that I've done on the GS. I did check the O2 sensors manually using an oscilloscope.

I've experience O2 sensors gone bad between 110K -150K on other Lexus and Toyota.

ibidu1

iTrader: (1)

Did you test the o2 sensors manually with a volt meter before replacing them? With a volt meter set it at 200 ohms, and check the connection on the 2 black wires, thats your heating circuit. If it shows an open circuit then that heating element is open and bad. If it shows resistance then it is good.

But I am still suspicious of how all your sensors went bad around the same time. Maybe you have a bad ground to the harness causing them to loose connection or foul up your o2 sensors.

My 08 GS350 awd is at 190k on original sensors

bossens

Dude, its probably bad cats. Do you burn oil?

I wouldn't think its sensors, replacing them just makes the code go away for a little while.