Recurring P0140 Code

Posted by TheRock0720, Mar 5, 2011
420A Bolt-on Tech - Intake, exhaust, ignition, fuel system, cooling, etc - specific to 2G N/T DSMs. New Members must limit their 420A tech posts to this forum.

  1. TheRock0720

    TheRock0720 Proven Member

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    Hey Forum,

    I've been getting this code, P0140 - Downstream HO2 Sensor Stays at Center, on and off for the past couple months.

    Tuesday 3-1-2011:
    I was about to go get my car inspected and the check engine light came on... So I had to cancel the appointment. I checked the code and it was P0140 (listed twice?). I drove around and back home, then went out later that day for a drive around the roads and then filled my gas tank. About a mile after filling up I was sitting at a red light and I noticed the CEL went out, so I continued onto the highway about about a mile down the highway the light came back on. The light stayed on from here.

    Wednesday 3-2-2011:
    CEL was still on (same code).

    Thursday 3-3-2011:
    CEL went out in the morning when I started my car and stayed off for the rest of the day.

    Friday 3-4-2011:
    CEL is still off, and has been off, for the whole day. I finally deleted the code, P0140, when I got home from work. Hasn't come back on yet..

    Saturday 3-5-2011:
    Unknown yet... :hyper:


    I have heard that the P0140 (Downstream HO2 Sensor Stays at Center) doesn't necessarily mean that your Rear O2 Sensor is bad, but it seems to be more common that there could be a wiring/ground/short issue with the wiring between the Rear O2 Sensor and the PCM.


    Don't like posting links to other forums, but this one has what I am referring to above. ^
    P0140 O2 Sensor??

    Also, as you know, I deleted the code last night, and I am going to get my car inspected today. Since I deleted the code, will they see that and fail me or?? I know my friends Honda passed, he deleted the code right before he pulled into the bay. I also have a Chevy Lumina that was throwing a code and I deleted the code before I went to inspection and it passed. So I know it depends on the manufacture, thats why I am not sure about Mitsubishi.
    #1
  2. razrman8

    razrman8 Proven Member

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    Well what you can do now is just a visual inspection, yourself, of underneath the car. Check the o2 sensors wiring and trace it back as far as you can to ensure that your wires are not messed up or damaged. That is what I would do

    As far as erasing the code to get it inspected, they will not be able to see that it has been cleared. If it is not on during the inspection then you should be alright. I have done it before, my car throws a EGR Flow Malfunction code when it wants to. Clear it, inspect it, you're good.
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  3. TheRock0720

    TheRock0720 Proven Member

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    Thank you, I will check one last time to make sure there isn't anything "out of place" and for the wires.

    P.S.- Sweet looking car! I love your rims, what are they?
    #3
  4. razrman8

    razrman8 Proven Member

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    No problem. Thank you. They are Rx-8 wheels.
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  5. bullettdsm

    bullettdsm N/T DSM Wiseman

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    As for erasing codes; you will probably come up with a NR (not ready) for that code you erased (unless you have driven it enough so that it could cycle). I'm hoping that you erased just that cel as opposed to choosing erasing all. If you erase all, you should have to wait for all processes to cycle (some cycle quicker than others based on their criteria)). That will give you a possibility that you may have more than one NR. In CT (for my 97) I was allowed two NR's (which was cool because I had two, LOL). I'm not sure what their parameters are in N.H.

    MB
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  6. TheRock0720

    TheRock0720 Proven Member

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    Alright I did go for inspection, and it did fail because 5 out of the 8ish sensors weren't ready to be tested. So I drove on Highway, Side roads, main streets, etc etc for totaling about 115 miles (I also shut the car off a few times in that 115 miles). I hope it passes now (going to get it inspected one more time tonight).

    Does anyone know what the OBD Cycle is for our 1999 Eclipses?

    UPDATE- Car will not pass with Check Engine Light on, a durr, I have the same code P0140 showing up. Wasted 100 + miles of gas for nothing. Getting new O2 sensor installed Monday.

    _______________________________________________________________________________________________________


    Any suggestions on the brand I should go with for the Rear O2 Sensor?

    Also, P0140 doesn't necessarily mean the O2 sensor is bad, there could be a short in the circuit, correct? So any common places that people have came across?
    Last edited: Mar 6, 2011
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  7. TheRock0720

    TheRock0720 Proven Member

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    Alright my car failed again today. After replacing the rear O2 sensor and 175 miles of driving and key cycles, the code is still popping up...

    Are there known shorts in the circuit with my car for the rear O2 sensor?
    #7
  8. Doug99RS

    Doug99RS DSM N/T Wiseman

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    What type of sensor did you install in there and have you verified that the light is coming back on for the exact same code or a new one related to the same sensor?

    Your first post describing the on-off-on light issue is really simple to explain. You had two P0140 codes in there because one was pending and one was active. Meaning... you had a hard fault that caused the light to come on in the first place and the pending meant that the sensor was tested again and would likely fail on the following test as well.

    If your area does plug-in testing then a hard fault code or even a pending fault code will cause a failure, the only way you'll get through inspection is with no codes and all or most of the readiness monitors set.

    The drive cycles for the mitsus are a pita, you just have to drive them in normal people mode for 60-80 miles and not in tuner mode.
    #8
  9. TheRock0720

    TheRock0720 Proven Member

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    We tested the old O2 sensor, and it was stuck at .45 volts and would not move. So we replaced the O2 sensor with a brand new one, and checked it out on the graph and volts and it was moving and responding as it should.

    After replacing the sensor with a new one, we drove it and then deleted the code with our code reader.

    I drove the car for about 150 miles (probably 10 key cycles or more) and took it to the inspection station. They hooked it up and mostly all the sensors we're up and running but the code P0140 was there (which is the same code I have been getting).

    I am setting up an appointment for Monday 3-14-11 to get my car checked out further by my mechanic.
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  10. Doug99RS

    Doug99RS DSM N/T Wiseman

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    There's a variety of "Brand new" sensors and I was specifically wanting to know what brand and what style. Was it Mitsu direct plug in, Bosch plug-in or universal-you-wire-it-up?
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  11. TheRock0720

    TheRock0720 Proven Member

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    I don't know exactly which one he put in. I believe it was after market, but thats about all I know..
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  12. Doug99RS

    Doug99RS DSM N/T Wiseman

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    If it was a plug-n-play then your chances of it being acceptable are decent. If it was a universal that he had to wire in himself then your chances are low.
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  13. TheRock0720

    TheRock0720 Proven Member

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    It was a "plug-n-play", the testing and install took a total of about 45 mins or less.
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  14. bullettdsm

    bullettdsm N/T DSM Wiseman

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    Did you check your cat and your exhaust? Could be a bad cat or an exhaust leak (before the cat). What your rear O2 is there for, is basically to check the cat. If you have an exhaust leak or a bad cat, the expected values of the rear O2 may not match and may throw a rear O2 sensor code.

    MB
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  15. TheRock0720

    TheRock0720 Proven Member

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    Sorry I did forget to mention, I recently installed a new direct fit cat because I was getting a P0420 code. My exhaust is pretty solid, there was one minor leak, but we patched it up and doesn't seem to be an issue.
    #15
  16. VelocitàPaola

    VelocitàPaola DSM N/T Moderator

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    Are you sure this new catalytic converter is actually a catalytic converter? A lot of "high flow" cats on eBay are actually just hollow tubes. Even actual high flow cats can trip a downstream O2 sensor code.
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  17. TheRock0720

    TheRock0720 Proven Member

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    Advance Auto Parts: Catalytic Converter - ULTRA Direct Fit by Walker - Part 15848

    That is the Cat that I bought and installed. ^^
    #17
  18. Doug99RS

    Doug99RS DSM N/T Wiseman

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    Is this code something new that has shown up since the cat replacement or was this code there as well as the p0420?

    Did you have to heat anything like the cat bolts or oxygen sensor to replace the cat?
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  19. TheRock0720

    TheRock0720 Proven Member

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    The code P0140 was coming and going along with the P0420 code. So the P0140 code was present before the P0420.

    And I didn't have to heat anything up to remove the old cat.
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  20. TheRock0720

    TheRock0720 Proven Member

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    Any other suggestions, forum?
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  21. VelocitàPaola

    VelocitàPaola DSM N/T Moderator

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    Please don't bump your threads. As a proven member, you should know better.
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  22. Shake_Zulla

    Shake_Zulla Proven Member

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    I hate emissions stuff and am no expert but have you tried running 93 octane? It might get you a more complete burn and be just enough to be able to reset your codes and keep it off untill you can get tested. Maybe new spark plugs too? Just trying to think outside the box here. The time I had a problem with my old Eclipse I asked the guys at the testing place if they could put the sniffer on my car and run it then they gave me the numbers and I had a better idea of what needed to be done to pass.
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  23. TheRock0720

    TheRock0720 Proven Member

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    Funny thing, when I first got this Eclipse back at the end of October of 2010 I put some 93 gas along with some Lucas Fuel Treatment and thats when I seemed to first get the codes. But I usually run 87 because gas is 3.40 here...and thats plenty.

    But my mechanic is trying to find out what the common issues are with these eclipses are with this P0140 code so he doesn't rack up a bill just testing everything. So thats why I was hoping you guys would have good information...
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  24. Shake_Zulla

    Shake_Zulla Proven Member

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    Do you remember if the Lucas was an alcohol based solvent cleaner and how many times did you put it in? The reason why I ask is a lot of treatments have alcohol based solvents in it (IE ethanol, methanol, isoproply alcohol) and will damage engine parts if used on every tank of gas. Now as far as what specifically it damages I'm not sure. I read somewhere that it burns too hot but I can't remember where so just a heads up.

    By the way... The difference between $3.40 and $3.60 on a 17 gal tanks is $3.40 total... be good to your car and give it what it wants :D Or do whatever you want I'm just jealous you can get 93 at the pump... lucky sob.
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  25. TheRock0720

    TheRock0720 Proven Member

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    Yes I do know about alcohol and its alcohol based, I do add "dry gas" to my tank as well to keep everything in check. I haven't done Lucas in a few months, I still have some left, so when I get down to a quarter of a tank I'll fill up at 93 and throw some of that Lucas in there and see how she does.
    #25

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