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CEL code P0138

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Cip, Feb 17, 2012.

  1. Cip

    Cip Junior Member

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    Check Engine Light - Code P0138 and others

    I saw other threads on P0138 but mine is a little bit different.

    I shipped my Prius from US to Eastern Europe. Here the winter was an unusually tough one. A lot of snow and temps even as low as -10F.

    About a week ago, while driving through some snow, my CEL came on. I turned off the engine, turn on ... and noticed that my "Maint Reqd" light also bliked for 5-6 times. So I said it's the oil change reminder ... maybe the CEL is related.
    I reseted the Maint Reqd, then I disconected the battery to reset the CEL too.

    For a couple of days I was happy, I drove carefully, no CEL.

    But one day, again that day I think I hit some snow bank, the CEL came on again. So I connected my ELM327 blutooth scan tool and after getting no code with some softs and getting P0101 by another, I got P0138 with scantool.net and with masterscan. So I think this is it, P0138. It's probably related to some Oxygen sensor.

    Now, is this serious, what happens if I drive it like this!?
    I am reluctant to go to the dealer, since they will charge a lot only to look at me.
    So, where should I look first? What to do? Is this related to MAF anyhow?

    I checked my air filter and looks fine. The oil level is fine. Under the body I cannot see much. There is some snow here and there collected. There is the Fumoto oil valve sticking out, easy to be hit by some snow/ice. I really suspect it's something due to ice/snow rather than faulty O2 sensor (which ntw I have no idea where it is placed).
    Any advice where to start?
    Thanks a lot!
     
    #1 Cip, Feb 17, 2012
  2. firepa63

    firepa63 Former Prius Owner

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    DTC P0136: OXYGEN SENSOR CIRCUIT MALFUNCTION (BANK 1 SENSOR 2), DTC P0137: OXYGEN SENSOR CIRCUIT LOW VOLTAGE (BANK 1 SENSOR 2), DTC P0138: OXYGEN SENSOR CIRCUIT HIGH VOLTAGE (BANK 1 SENSOR 2)
    The heated oxygen sensor is used to monitor oxygen concentration in the exhaust gas. For optimum catalytic converter operation, the air-fuel mixture must be maintained near the ideal "stoichiometric" ratio. The oxygen sensor output voltage changes suddenly in the vicinity of the stoichiometric ratio. The ECM adjusts the fuel injection time so that the air-fuel ratio is nearly stoichiometric ratio.
    When the air-fuel ratio becomes LEAN, the oxygen concentration in the exhaust gas increases. The heated oxygen sensor informs the ECM of the LEAN condition (low voltage, i.e. less than 0.45 V).
    When the air-fuel ratio is RICHER than the stoichiometric air-fuel ratio, the oxygen will be vanished from the exhaust gas. The heated oxygen sensor informs the ECM of the RICH condition (high voltage, i.e. more than 0.45 V).
    The heated oxygen sensor includes a heater which heats the zirconia element. The heater is controlled by the ECM. When the intake air volume is low (the temperature of the exhaust gas is low), current flows to the heater in order to heat the sensor for the accurate oxygen concentration detection.
     
    #2 firepa63, Feb 17, 2012
  3. Cip

    Cip Junior Member

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    Re: Check Engine Light - Code P0138

    OK, a few hours later I tried a different scanmaster version and the codes are different:
    P0029 - Exhaust Valve Control SOlenoid Circuit Range/Performance
    P0120 - Throttle Position Sensor/Switch (TPS) A Circuit Malfunction

    Plus I get some info that the Catalyst/Evaporative System and Oxygen Sensor do not work properly.
    I am attaching 2 snapshots.

    Now I am getting really worried!
    I wonder if it is something physical related to hitting some snow bank or maybe it has to do with the gas quality (this happened after my last fill).
     

    Attached Files:

    #3 Cip, Feb 17, 2012
  4. Cip

    Cip Junior Member

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    Thanks firepa63, your description is welcome but is very technical.
    I still do not understand if this is bad or I can still drive around like this.
    Or what can I do myself about it?
    Thanks!
     
    #4 Cip, Feb 17, 2012
  5. firepa63

    firepa63 Former Prius Owner

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    Is the fuel you're using the same octane as what you used in the US?
     
    #5 firepa63, Feb 17, 2012
  6. Cip

    Cip Junior Member

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    I am not sure, they call it 95. It's the lowest here.
    But what I am thinking is maybe the quality of the particular fill due to the heavy snowing.
     
    #6 Cip, Feb 17, 2012
  7. Cip

    Cip Junior Member

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    At this point, with the codes and messages I have in the images I posted, after I started to understand where and what the pieces are, I am pretty sure something happened when the cat hit some snow bank. Maybe there is some snow or ice gathered underneath ... I guess I'll go to a local garage and try to inspect it and clean the snow and ice.
    This experience helped me in making an idea what is what:
    http://www.pbase.com/kocho/exhaust_prius&page=3
     
    #7 Cip, Feb 18, 2012
  8. seilerts

    seilerts Battery Curmudgeon

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    I think you have an electrical fault. Many of these sensors share a common ground point. Inspect all areas of the engine compartment and underneath the car for wiring damage. You should not be able to get P0029 on a 2005 either.

    Use the graphic capability of your scan tool to plot the action of the O2 sensors while you are driving. That will give you better information about them and the converter. I don't think you need a converter.
     
    #8 seilerts, Feb 18, 2012
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  9. kohnen

    kohnen Grumpy, Cranky Senior Member

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    Eastern Europe: Do they still use lead in their gas? If so, these could be the indications that the emissions system is being poisoned.
     
    #9 kohnen, Feb 18, 2012
  10. Cip

    Cip Junior Member

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    Nope! Btw, I know at least 5 people with Prius around here (one brought from US) ... they use the same regular gas.
     
    #10 Cip, Feb 18, 2012
  11. Cip

    Cip Junior Member

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    I read that the first O2 sensor should swing around .5V and the second should show about constant .7V. Is that right?
    http://www.autoshop101.com/forms/Hybrid12.pdf

    http://share.qclt.com/丰田普瑞斯原厂英文手册PDF格式/Repair Manual/04pruisr/05/2054m/cip0136.pdf

    Today I checked again and the scanmaster v2.1 software showed P0138. Tomorrow I'll try to get underneath and also check the O2 wave(s).



     
    #11 Cip, Feb 19, 2012
  12. seilerts

    seilerts Battery Curmudgeon

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    The Prius is different. The upstream O2 will read around 3.3V+/-. The downstream should be 0.5V+/-. P0138 means the downstream reads high, never going below 0.6V during the active test. The ECM is measuring a voltage drop, er, well, the impedance, but anyway, if the element is defective (low impedance) or the wiring is faulty (short circuit), then it will set this.
     
    #12 seilerts, Feb 19, 2012
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  13. Cip

    Cip Junior Member

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    It has been a while, the weather is now better, but still not very warm, about 5Celsius.

    I took the car to a local mechanic, we could not find anything apparently wrong beneath. The O2 sensor looks fine mechanically.

    I tried clearing the code. The P0138 disappeared, but the P0031 remained. About P0031 I read here:
    http://www.obd-codes.com/p0031
    However it looks like my sensor shows about .9V ... when I start the engine it stays at 0 for a bout 2 minutes and then it goes up slowly ... in about 1min it gets around .9V .935 .955, sometimes when I accelerate suddenly goes lower but then goes back.

    I am not sure what to do next, other than wait a while for the spring to come and take a longer ride. Because I only drive a few miles per day and at relative low speeds. Should I be really worried about P0031?

    I attached some snaps.
     

    Attached Files:

    #13 Cip, Mar 14, 2012
  14. Cip

    Cip Junior Member

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    It looks what happened to me is similar to here:
    http://priuschat.com/forums/gen-ii-...ng/89631-oxygen-sensor-code-cold-weather.html

    So, the upstream sensor is the A/F ratio? Is that the one I am reading about 0.9V.
    Does it look like I need to test/change the A/F ratio sensor? Or other causes may apply too?
    Thanks!

    http://priuschat.com/forums/gen-ii-...ting/89967-oxygen-sensor-collar-around-3.html

    http://priuschat.com/forums/toyota-...s-tsbs/77210-o2-air-fuel-ratio-sensors-3.html

    http://priuschat.com/forums/gen-ii-...on/96929-location-oxygen-sensor-bank-2-a.html
     
    #14 Cip, Mar 15, 2012
  15. Cip

    Cip Junior Member

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    I still have the P0031, so I want to buy an A/F sensor, since it's most probably its fault.
    However, can anyone ensure me I'm looking for the right part? Which from the list bellow is the best option for my 2005 Prius? The part no. seems to be 89467-47010.
    Later edit: Denso 234-9056 seems to be the right replacement. Am I right?

    1. 2006 Toyota Prius - DENSO 234-9056 Air- Fuel Ratio Sensor

    2. http://www.amazon.com/04-07-Toyota-Oxygen-Sensor-8946747010/dp/B005KGAM52

    3. 04-07 Toyota Prius 1.5L Air Fuel Ratio Oxygen Sensor | eBay

    4. Toyota PRIUS Oxygen Sensor - Genuine Auto Parts

    5. 89467-47010 - OEM Toyota SENSOR, AIR FUEL RAT


    Or if anyone knows a better place/price...



    This is probably not A/F pre-catalitic sensor as stated and which I need, but the post-catalitic O2 sensor:

    6.http://www.amazon.com/dp/product/B000C5WCUO?tag=priuschatcom-20 the tool I'm looking at

    A. http://www.amazon.com/gp/product/B005LTJ01U?&tag=shopwiki-us-20&linkCode=as2&camp=1789&creative=9325

    or

    B. Universal O2 Oxygen Sensor Socket 7/8" 22mm 6pt 3/8"Dr | eBay

    although I know they are not exact fit.
     
    #15 Cip, Apr 20, 2012
  16. Cip

    Cip Junior Member

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    So, I replaced about a month ago the AF sensor with a Denso 234-9056 (which btw was reduced by Amazon to $60 right after I paid $100 for it). I did it at a local garage, working together with the electrician. My long thin arm was very useful ... otherwise I don't see how we could do it. The 7/8" tool was helpful but needed some thinning. So far the code is gone. I should read the sensor values now to compare with the ones given by the faulty sensor.

    Now I got the Christmas tree stalling problem ... with the red triangle and exclamation sign and everything. I replaced the 7 years old original battery with a Varta B33, but no good. After all, I was able to read the inverter water pump code P0A93. The coolant also is not bubbling in the container. So a water pump is already in the mail. I plan to replace it myself as shown here. It seems doable... I need to document some more and move the discussion here anyway.
     
    #16 Cip, Jul 24, 2012
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