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As several of the regular forum members can see, I have been posting a number of recent questions lately. I have several other Lexus V8s but this little RX300 is new to me. Got it for my son. I am truly amazed at the level of detail and quality that went into this vehicle. My wife had a 2014 RX350 for a few years on a lease, but that car never resonated with me. This little gem, however, is simply well made with a ton of attention to the little details.
The car I acquired has 212K and was for the most part a one/two owner. An elderly woman had it until 189K then gave it to her daughter. I have 20 pages of Lexus service work which I reviewed recently. It has never been in an accident and in very good condition.
I am going through a number of little fixes right now.
The following codes popped up.
1) P0174 was the MAF sensor. It was replaced at around 80K. I took it out and cleaned per all the suggestions. It is not showing the code now.
2) P01130 O2 Sensor ( BANK 1 SENSOR 1) 89467-48011
3) P01150 AF Sensor - ( BANK 2 SENSOR 1) ARE THESE THE SAME PART NUMBERS?
I just spoke to the Lexus dealer and he said since these are both SENSOR 1s, that these are AIR FUEL SENSORS NOT O2 sensors. Both parts are the same.
The Dealer Sensors are over $300 and some Denso's are about 1/4 that on EBAY, but who knows if they are fake? How important is it to get OEM or can I just order an inexpensive aftermarket? If not is there a lesser expensive solution.
Your fuel trims are way out on both banks- when fuel trims are positive this means the affected bank is running lean and the ecm must add fuel to compensate.
If you can rule out a vacuum leak at idle using a vacuum gauge only as a way to 100% prove no vacuum leaks, maybe bad A/F sensors?
Maxsteel's list above includes other possible issues too.
Vacuum gauge is only $15(harbor freight) and so much cheaper than throwing 2 or 3 oem sensors at it "parts canon" style, just thinking outloud...
Thanks for all the tips. Just to add a few other observations. I do not notice any issues with acceleration or power.
I do hear a slightly louder than normal sound on the back of the engine... sounds kinda like it could be an exhaust leak.
Having a mechanic look at it over the weekend when he installs the rear struts. I purchased the FCS Struts from Rockauto... and will report back after the install.
By the way, there are several sellers on EBAY that are offering genuine Denso sensors for 1/3 of what the dealer quoted me. Wonder if they are real?
Another possibility I suppose is you could still have a MAF problem but it isn't throwing a code.
I think you can test it with an ohmmeter
Great video above and he is spot on.
Your mechanic will verify any vacuum & exhaust leaks and misfires before throwing A/F and O2 sensors at it, you can be sure.
Then the sensors will do their best to hit stoich but there is a limit as to how much they can correct before ecm throws all kinds of codes.
Also, on our cars the ecm doesn't send a nice waveform like that to the scanner- the ecm converts sensor current to a scaled voltage unfortunately(the way I understand it)- I wish it did so we can see it!
Great video above and he is spot on.
Your mechanic will verify any vacuum & exhaust leaks and misfires before throwing A/F and O2 sensors at it, you can be sure.
Then the sensors will do their best to hit stoich but there is a limit as to how much they can correct before ecm throws all kinds of codes.
According to Lexus Repair Manual, there are 1 Oxygen sensor, and 2 Air/Fuel Ratio sensors in 2000 Lexus RX300.
Attached files "3.pdf" shows their positions ( borrowed from 81corolla )
Bank 2 A/F sensor is near the radiator, and bank 1 A/F one is near the firewall. Replacement for both of them are Denso 234-9009, and for Oxygen sensor, Denso 234-4215.
I am having a Toyota Mechanic check it out tomorrow.
I got under the vehicle after having read a few other issues these cars have and noticed my exhaust flex hose is deteriorated and will either need to be replaced or a new mesh piece will need to be spliced then welded in. Could this through off any codes?
I am having a Toyota Mechanic check it out tomorrow.
I got under the vehicle after having read a few other issues these cars have and noticed my exhaust flex hose is deteriorated and will either need to be replaced or a new mesh piece will need to be spliced then welded in. Could this through off any codes?
Yes it can. You may have failing sensors too from from age and miles but any leak before an O2 sensor can cause craziness, whether intake or exhaust.
Maxsteel's video above covers this theory very well in detail of leaks before sensors.
99RX300PDX's drawing shows the location of the rear downstream O2 sensor and when compared to a location flex pipe leak, it can be seen a leak here is before the sensor.
Wishing you success, plz let us know how it goes!
09-28-21, 12:43 PM
P01130 O2 Sensor and P01150 AF Sensor
