The other day I was able to get a code check on my 2000 RX300. The codes displayed are P0125, P1130 and P1135.
Do I need to replace both Fuel Air Ratio Sensors and the O2 Sensor or can I just replace the Air Fuel Ratio Sensors, reset the code reader, and see what happens?
From what I have been able to read the A/F Ratio Sensor is either Lexus P/N 89467-48011 or Denso P/N 234-9009. The O2 Sensor is Lexus P/N 234-4215 but I do not have the Denso P/N.

Thank you for any help available.

Bearbrew

 

Yes, the 234-9009 is the one for either of the two upstream a/f sensors coming off the exhaust manifold. The O2 sensor (one after the main cat below the vehicle) most likely will not need replacement. The O2 sensor also is not critical to the function of the vehicle, just it's emissions, so it can be looked at later if either one or both of the a/f sensors need replacement.

For now, go ahead and reset the code reader and see what happens.

With the Elmscan5 Compact I just got, I am able to read the values on the sensors and do get A/F sensors myself (given my RX's modifications), but they come and go, but I can see where the values are way off or on target. But if your scanner can't read these, best to reset and see if these codes come back or not.

 

Today I will reset the codes and see what happens. If the codes reappear I will replace the Fuel Air Ratio Sensors.
The P0125 code has me concerned. Perhaps it will be corrected by replacing the A/F Ratio Sensors.

Thank you for the information,

Bearbrew

 

I was in your situation, but with the Bank 2 a/f sensor. If I were you I would clear the codes and wait for them to reappear. Assuming that you get at least the 1130/1135 then replace the Bank 1 sensor only; its the one closest to the firewall. I predict that once that is done the 125 code will not reappear.

 

From what I have read, here on the forum, that sound like the way to go. As has been stated, the back manifold sensor gets more heat and is the one most likely to be the problem.

Bearbrew

 

Just completed the order for a Denso A/F Ratio Sensor, P/N 234-9009, from Amazon.com. Their price was $119.76 which is a lot better than any other place I could find.

Bearbrew

 

Yeah, I paid about $120 also; MSRP from dealer was $300.

 

One of the big problems with the RX300 and it's 1MZFE engine is the precats stuck very far up the pipes close to the exhaust manifolds on each bank. If you take a look at a 5 speed Solara first generation, it doesn't have these precats and it's also a 1MZFE, I don't see too many people with those having a/f sensor issues. (it's a federal-spec vs. cali-spec thing along with 5 speed vs. auto). In later model RXs from my personal inspection, the precats were put a bit further down the pipe and I think that has no doubt helped the longevity of the a/f sensors.

Yes, Bank 1 behind the engine block definitely gets the most heat.