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Toyota Repair/Code P0138


QUESTION: 2007 Rav4,115,000 miles, 4 cyl. 2.4L.  Code P0138, Oxygen sensor high voltage, Bank 1 Sensor 2.   Changed O2 sensor, downstream after the cat converter,  with a Bosch OEM plug style sensor. One replaced was 2 years old, had 35,000 miles on it.  Cleared the code and comes back up again, same code. Getting 0 to .9V, sometimes more output..Bank 1 Sensor 2 short term fuel trim.. I unplugged the sensor, ran it, got code for low voltage code P0137, which is what I should get, meaning wiring is OK ??  I have correct ohms reading 11-16 ohms between terminal 1 (HT1B) and terminal 2 (B+) on sensor .  Have 12V at sensor connector B+. Coolant temp 192F.  Catalyst temp B1S1- 1342 F and B1S2- 1133 F. Do I need to check the wiring, for short, open, continuity from sensor connector and ECM connector?  Could the Bank 1 Sensor 1 A/F sensor be bad even though it's not coming up ??  The engine is running fine..  Anything else I can do before getting into the wiring ??..Have access to scanners with O2 readouts, etc..  Thanks

ANSWER: Hello, standing in front of the car which sensor was replaced? On the 2 AZ-FE bank 1 is on the right side, was this one replaced. If this is correct please provide A/F ratio sensor voltages and #2 O2 sensor voltages for bank one, Also fuel trim readings would help for bank1, thanks.

---------- FOLLOW-UP ----------

QUESTION: The sensor I changed was downstream, B1S2,lower O2 sensor, under the vehicle, in exhaust pipe, in the middle of the car I guess.  Do you want current readings or try to get readings at time of malfunction ?  thanks

ANSWER: Thanks current readings would be ok for now, is the the PZEV or non PZEV engine, you can tell by the location of the A?F ratio sensor which is on top of the manifold and there is no heat shield, this is the PZEV engine.

---------- FOLLOW-UP ----------

QUESTION: There Is a heat shield on the manifold & AF sensor is just below the shield:
         Freeze Frame Error   Now code cleared idle.
O2S B1-S2 V- .86          .78
AFS B1-S1 V- 3.64          3.24-3.33
Total FT#1- .07          .04
Short FT #1 (%)-2.31          3.87
Long FT #1 (%)-7.00          .03
O2 FT B1-S2 (%)- 99.2          99.2
AF FT B1-S1 (%)- 1.057          .999-1.00
Hope this helps,  Thanks, George

Thanks, I don't see anything wrong here but I assume this is after the code was cleared, the A/FS voltage is a little high in the freeze frame data but ok now. When monitoring the rear O2 sensor does it respond when revving the engine, the voltage should not go over .999 volts if it does then it's why you're getting the P0138 code. See what it does at a steady 2000 rpm.

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Ted Ritter


I have more than 28 years experience as toyota technician, I will be able to answer most questions related to the Toyota product line up to the present year models,I am located in the US but welcome questions from other regions of the world. When asking a question please provide specific information: year,model, engine,transmission information. Provide as much information as possible including a brief repair history if possible. I have been a volunteer here for more ten years an have answered over 16,000 questions helping Toyota owners with their problems and save thousands of dollars without any compensation, some of my answers are published on many other websites including google and various automotive forums. DONATIONS ARE VERY MUCH APPRECIATED, IF YOU HAVE RECIEVED HELPFUL INFORMATION PLEASE MAKE A DONATION. AS OF TODAY (JULY 22, 2014) ALL REQUESTED GRAPHICS, ILLUSTRATIONS, DIAGRAMS, PHOTOS, WILL REQUIRE THE MINUMUM DONATION UP FRONT.


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