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Genchi Genbutsu
Genchi Genbutsu, Toyota Master Technician
Category: Toyota
Satisfied Customers: 4395
Experience:  Toyota Certified Master Diagnostic Technician, ASE Master Technician with L1 Advanced Engine
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I have a 2002 Toyota Rav4. Two months ago I had all four

Customer Question

I have a 2002 Toyota Rav4. Two months ago I had all four oxygen sensors replaced. Over the weekend, I got a code, P1150. It is my understanding that this is the rear most downstream O2 sensor. What would cause this?
Submitted: 1 year ago.
Category: Toyota
Expert:  Genchi Genbutsu replied 1 year ago.

Thank you for allowing me to help you with this concern today and am sorry to hear that this is happening. I will have to ask you a few questions so that I can get a better understanding as to what may be going on with your Rav4.

The P1150 code is for Bank 2 Sensor 1 which is located (as you are standing at the front bumper, hood open, looking at the engine) the upper left sensor.

What brand sensor did you install the first time?

Customer: replied 1 year ago.
All four sensors are OE Denso
Expert:  Genchi Genbutsu replied 1 year ago.

I see. Are you performing the work or is a repair shop?

Did you make sure that the sensor connector is plugged in fully seated and clean of debris?

Customer: replied 1 year ago.
The work was already done, and dielectric grease was used on all electrical connections.
Expert:  Genchi Genbutsu replied 1 year ago.

The dielectric grease is not something we usually see at the Dealer so this job was performed by an Owner or an Independent Repair shop. You will want to just double check on that and make sure it's good to go. The next step would be to clear the codes and see if that specific code returns. It code be just a fluke but if it did return then you will have to look deeper into the wiring harness and the Engine ECU as the cause.

Have you tried clearing it and seeing if the code returned yet?

Customer: replied 1 year ago.
I have a diagnostic scanner, but I have not cleared the code. I tend to use dielectric grease on all connections, as in Wisconsin, winters are rough and there is a lot of road salt used. I can try to clear it, just wondering why if they are all brand new OEM sensors why there would be an issue. ECM is new and latest software has been flashed.
Expert:  Genchi Genbutsu replied 1 year ago.

I have not cleared the code. I tend to use dielectric grease on all connections, as in Wisconsin, winters are rough and there is a lot of road salt used

I see. Please keep in mind that I'm not saying the grease is the cause and I understand the environment situation but based on my experience at the Dealer and with Toyota Engineers, it would be recommended to clean the grease off, clear the code and see if it returned. If it did then check the resistance of the wires from the engine ECU to the B2S1 sensor first as we rarely see any issues from these computers. Most likely, if the code does return, you will find excessive resistance in one or more of the wires from the ECU to the connector. You are dealing with a circuit/performance code.