Engine code P0126: Engine Temp insufficient?

Discussion in 'The Garage' started by JEDI, Dec 19, 2011.

  1. JEDI

    JEDI Lifer

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    2005 Mazda3i Automatic, 130k miles

    got the check engine light this morning. i then noticed that my temperature gauge is a little lower than normal.

    From OBD II reader:
    PO126 coolant temp insufficient for stable operation.
    coolant = 147F, outside Temp = 30F


    So how does this affect me, if any?

    And how do i fix it?

    THX!
     
  2. GuitarDaddy

    GuitarDaddy Lifer

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    The main downside to low coolant temps is your heater won't heat very well. Low temps can also effect the wear of critical engine parts over time as they are designed to operate at around 180 degrees, but this is a very low risk IMO. It can also decrease gas mileage slightly.

    I'm guessing the cause is your thermostat is stuck in the open position. The thermostat is usually a really easy part to remove and check, and inexpensive to replace.

    Remove it when the engine is cool and it should be in the closed position, if not its stuck in the open position. To further test the thermostat put it in c pan of water on the stove and heat the water, you should be able to see the thermostat open at around 180 deg, and when you turn the stove off and the water cools you should see it close again.


    After goggling around abit it seems this is a common problem on Masda 3's and a new thermostat is the fix. It appears that the thermostat on these cars is in a tighter than normal spot and may require removing the idler pulley to get easier access to it, although many claimed to be able to change it without doing so using an 8mm wobble(universal) socket.

    Damn on most cars a thermo is $4-10, but evidently Mazda makes you change the housing also, cheapest I can find is $28 at rockauto
    http://www.rockauto.com/catalog/raf...&partkey=1145630&a=FRc1433045k1145630-1897937
     
    #2 GuitarDaddy, Dec 19, 2011
    Last edited: Dec 19, 2011
  3. JEDI

    JEDI Lifer

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    thx!

    when i popped the hood after work today, i noticed the coolant level barely below the minimum mark.

    would that trigger the code?
     
  4. MiataNC

    MiataNC Platinum Member

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    Engine temperature has a direct influence on emissions. That specific code is set when the engine temp does not reach a predetermined "proper operating temperature" within a specific amount of time.

    I think the previous post about your thermostat being stuck open is dead on.

    While a stuck open thermostat won't hurt the engine, it will certainly set the code you are seeing, because in colder weather the engine won't get hot enough to satisfy emissions requirements.
     
  5. JEDI

    JEDI Lifer

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    thx!

    my emmissions is in May. :)
    so no need to do anything?

    and how does this code lower my gas milage?
     
  6. AdamK47

    AdamK47 Lifer

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    My wifes 02 Monte Carlo SS throws this code 3 or 4 times during the Winter months. Always in the morning when the temps are in the teens or less and I haven't let the car warm up before leaving. The car gets warm eventually, but by that time I'm already at work. I clear the code with my OBD-II and forget about it.
     
  7. Ferzerp

    Ferzerp Diamond Member

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    Depending upon how cold it is, you may be running in open loop mode. A lot of the sensor feedback is ignored, and you lose a lot of the advanced ignition, fuel mix, etc controls, so yes, it's something you want to fix (also why it impacts mileage).
     
  8. SpatiallyAware

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    +1 on getting it fixed.


    Does it seem to take longer to warm up? Usually when the thermostat is stuck open it takes forever to warm up in the mornings..
     
  9. JEDI

    JEDI Lifer

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    no. warmed up like usual (under 5 min).

    drove it for like 15 min then the check engine lite came on.
    then I noticed the temp gauge lower than normal.
     
  10. bbs lm-r

    bbs lm-r Senior member

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    To help raise low coolant temps, your PCM is gonna command your injectors to stay open longer (drop more fuel) to build up heat.
     
  11. LTC8K6

    LTC8K6 Lifer

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    Engine oil may not reach the correct viscosity.
     
  12. EightySix Four

    EightySix Four Diamond Member

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    Negative ghost-rider. Engines run hotter when they are running a fuel-lean condition, not a fuel-rich condition.

    Engines fail emissions when they run too cool because they can not get the cat(s) up to temperature. Depending on the type of catalyst, low temperatures can actually increase harmful emissions. Also, for maximum efficiency you need a lot of parts in your engine need to heat and expand to create a proper seal.
     
    #12 EightySix Four, Dec 19, 2011
    Last edited: Dec 19, 2011
  13. bbs lm-r

    bbs lm-r Senior member

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    Completely understand what you're saying, as this method (add air to fire to make it hotter) is used in cars with AIR injection to purposely pump more oxygen into the exhaust at start-up to heat up the O2's and CAT(S) faster.

    But on a cold/cooler engine than normal (like OP's), I'm certain the injectors will open longer to drop more fuel to raise temps. Idle air/throttle is probably gonna be increased ofcourse to bring enough air to mix with the extra fuel, but the PCM is gonna command a rich mixture to raise temps, thus gas mileage might take a (small?) poop.
     
    #13 bbs lm-r, Dec 19, 2011
    Last edited: Dec 19, 2011
  14. LTC8K6

    LTC8K6 Lifer

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    A rich mixture should lower engine temps.
     
  15. EightySix Four

    EightySix Four Diamond Member

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    Sorry, that is still incorrect. An engine running rich is cooler than an engine running lean in pretty much every situation. I've been doing PCM tuning for at least long enough to know that ;)

    http://www.google.com/search?hl=en&...&gs_sm=e&gs_upl=0l0l1l29l0l0l0l0l0l0l0l0ll0l0
     
    #15 EightySix Four, Dec 19, 2011
    Last edited: Dec 19, 2011
  16. bbs lm-r

    bbs lm-r Senior member

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    Fair enough, Yrs of Exp > Yrs of Theory (w/ some exp) ;)

    Ok one more thing (I promise);

    cool engine in the morning, start-up AFR, what say you?
     
  17. EightySix Four

    EightySix Four Diamond Member

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    Generally cold starts are often rich because the fuel atomizes poorly when cold making a lean start harder, however this depends on the motor, for example I could start my Sky RL relatively lean because it was DI and the atomization was much more controlled than a port injection car. You also run richer in open-loop (start-up) because you're not getting accurate feedback from the O2 sensors until they are hot (narrow band O2s are inaccurate until warmed up) and then switch to closed-loop and hunt for stoich.

    So, yes, you cold start the motor rich because the goal isn't "get hot as quickly as possible" it is "make the motor start despite poor fuel atomization."
     
    #17 EightySix Four, Dec 19, 2011
    Last edited: Dec 19, 2011
  18. SparkyJJO

    SparkyJJO Lifer

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    Here's what can happen when running too cold:

    1) Computer sees the engine not up to temp yet, so it stays in open loop mode
    2) Open loop means it ignores the O2 sensors, so it runs rich to be sure it won't blow something up by going too lean.
    3) This extra fuel means your mpg drops (how badly it drops depends on the vehicle, some can drop as much as 5mpg).
    4) Emissions go up and over time can also lead to plugging up the catalytic converter, fouling the O2 sensors, etc.
    5) Plugged cat leads to even worse vehicle performance and even worse mpg

    All this bad stuff can be caused by a simple thermostat sticking open.

    So, yeah, don't let it go too long.
     
  19. EightySix Four

    EightySix Four Diamond Member

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    Even with a jammed thermostat I have never seen an engine stay that cold while operating for any reasonable period of time, but this scenario is certainly plausible. I guess the climate down here just isn't cold enough. Good call.