Guys,
My 2006 GS300 is throwing P2198, P0037 & P0138, the dealer is saying the ECU has to be replaced along with the O2 sensors because Lexus have changed the O2 sensor design into a cup style and the existing ECU has to be replaced to understand the new O2 sensor. Do you think replacing the existing O2 sensors with newer ones (Pre- the cup style design) will clear those errors?

the car has 150K miles on it, and it drives very smooth otherwise. Any suggestion?

 

I would defintely not change anything at that dealer. this sounds more like he doesn't know what he is doing. also why would that have been ok for the last 150k miles? p2198 means bank 2 sensor 1 is stuck in rich position. maybe check your injectors, if one of them is not closing properly. P0037 only means heater of oxygen sensor control circuit low.
P0138 means o2 voltage high...i would check the values again with an elm327 obd adapter and verify which sensor is doing what, then replace a sensor and also investigate in the fuel injector thing.
also have you ever used something like seafoam? as the 300 is a direct injection engine, it might have something to do with carbon deposits.

 

Thank you for your reply,
I've uploaded a pdf of the TSIB the dealer is talking about. I will definitely check the injector and see. I've never used seafoam, I will google it and see how to use it..

 

I would send off the ecu to get repaired cost is $115 all you do is send your ecu they repair it and send it back. But if the o2 sensors are what need to be replaced, replace them with the old style that lasted 150K miles

Many use these guys

https://www.ebay.com/itm/Lexus-GS300...frcectupt=true

 

these guys repair only ECUs with hard down-shift problem which I don't have...I am leaning toward the theory of a bad injector and / or replace those O2 sensors with the old style...RockAuto have those Walker brand...

 

If it were me, I'd replace the O2 sensors first, then clear the codes and then see what else pops up afterwards.

 

for sure, but i will change them with the older style only...

 

Actually they do general repairs but it sounds like your ecu is fine.

I would use Denso sensors over walker brand denso is what oem uses. Try replacing the o2 sensors and see, if you do not get anywhere then taking it to a good mechanic that has a good scanner that can see what the sensors are actually doing.

The fuel injectors more likely have nothing to do with o2 sensors going bad unless one is stuck open and just dumping fuel and more likely it would run really bad. I think the reason your o2 sensors went bad were probably from carbon buildup. I would pull off the intake manifold and manually clean the valves

 

Any easy way to diagnose a faulty fuel injector?...will it show from TechStream?

 

You can grab a long screwdriver put one end on the injector, the other end on your ear. You should hear a really fast ticking on each one. If you hear on all except for one or two then know that those are bad, and may just have a loose connection, or it maybe internally stuck. Sometimes gently tapping will allow them to fire back on. There are places that can clean and revive old injectors.

What kills O2 sensors is unburnt fuel, could be a stuck open injector, or really bad case of carbon not allowing the fuel to atomize. If you do not fix the issue, then your catalytic convertors can go out next. Like I said previous I think its carbon issue, pop off the intake manifold and do a manual cleaning and throw new spark plugs, and you should be fine.

 

Great.One final question, do you recommend the use of STP or seafoam cleaners? will they help?

 

I never tried the stp stuff so I cant compare, but seafoam is a good overall cleaner in my book.

 

I also have p2198 p2196 p0138 p0037 p2241 something about af sensor pumping Circuit?

I'm gonna replace those primary o2 sensors and I bet all the codes will go away, if not I'll check injectors and ecu. 3 of the injectors I got used from eBay(cheap)

 

I am going to test those O2 sensors myself with a good scanner and see what they are reporting and if they are actually bad or not...If your sensors are actually bad, then don't buy the cup style sensors because your existing ECU won't be able to read them...

 

I tested mine in live mode one of em is stuck at 3.3 so it's not being useful at all. Other one seems to be ok but there's still codes for it. My oil smells kinda like gas.

Cup style is for the downstream one?