Cel p0126

apple

As I was driving up CA Hwy 1 up the beautiful coast on my way to Monterey for a track day at Laguna Seca, a CEL came on.  The engine ran fine, so I assumed it was just an emissions thing...I have 85k miles on my MX-5 and suspected it may be a failing O2 sensor or a failing catalytic converter, so I didn't think too much of it.
I ran the track day yesterday and the car felt fine, so I didn't worry about it (I was going to get the code read but renting a code reader but stores don't loan out code readers anymore).
I decided to bite the bullet and buy a code reader today-- it pulled code P0126.  We looked it up on the Autozone computer and it said quot;Coolant thermostat condition--low operating temperaturequot;.  

The Autozone database also listed the possible causes:
-low coolant level
-open or short circuit condition
-faulty ECT Sensor (I don't know what an ECT sensor is)
I cleared the code (I still have a 600 mile trip ahead of me) so if this condition continues, the CEL should show up once again.
Any thoughts or experiences with P0126 ?

Hi
YOUR COOLANT THERMOSTAT IS STUCK OPEN. This is according to the Mazda Workshop Manual.

Thanks, John.  Would it need to be replaced or is it possible to manually close it?

Although I haven't gotten this code on the MX-5, I have gotten it on other cars.
I think Autozone is wrong...A low coolant would cause a High operating temperature.
I also don't think it is an open or a short, cause those usually will return a different code indicating that it is faulty.
My guess is that it is a broken thermostat, Part Guesstimate is about $10.00.
It might be a tuck thermostat as well however, if you are going to open it up to try and unstick it you are better off just replacing it, cause it will probably stick again.
If thermostat looks good then you will have to start checking other things, like the ECT (Engine Coolant Temperature) sensor itself, but start with the thermostat since it is a moving part the likes to fail!
If you need help locating the thermostat let me know and I can post a picture when I get home.


Originally Posted by jdrake4
I think Autozone is wrong...A low coolant would cause a High operating temperature.
I also don't think it is an open or a short, cause those usually will return a different code indicating that it is faulty.
My guess is that it is a broken thermostat, Part Guesstimate is about $10.00.
It might be a tuck thermostat as well however, if you are going to open it up to try and unstick it you are better off just replacing it, cause it will probably stick again.
If thermostat looks good then you will have to start checking other things, like the ECT (Engine Coolant Temperature) sensor itself, but start with the thermostat since it is a moving part the likes to fail!.

it actually can cause that code if you are out of coolant...when there is no coolant on the sensor it will read low because there's no coolant touching it! Don't ask me how I know  but lets just say that old ford ranger got a new headgasket...But then again if it is that low it wouldn't have survived the trackday.
It could also be a faulty sensor itself but it is indeed very unlikely. Thermostat springs wear out, and gum up overtime so it is very likely its just your $10 thermostat.
Mike


Originally Posted by mann
it actually can cause that code if you are out of coolant...when there is no coolant on the sensor it will read low because there's no coolant touching it! Don't ask me how I know  but lets just say that old ford ranger got a new headgasket...But then again if it is that low it wouldn't have survived the trackday.
It could also be a faulty sensor itself but it is indeed very unlikely. Thermostat springs wear out, and gum up overtime so it is very likely its just your $10 thermostat.
Mike

My Mistake.
You could get that error if the coolant is really really low...
I owned a Ford Ranger but luckily I never had that problem  !

Thanks guys.  I cleared the code, didn't actually touch anything, and drove approximately 600 miles yesterday and the code didn't come back.  I'm going to see if I can buy a little more FL-22 and top off the coolant reservoir (does anyone else find that thing hard to read with the large plastic seam in between the Full and Low marks?)  
According to the coolant gauge on the dash, the engine never ran hot, but then again, I don't know if the coolant temp gauge is a dummy gauge like the oil pressure gauge.
jdrake, if it's not too much trouble, could you please post a pic of the thermostat?


Originally Posted by lyrictenor1
I don't know if the coolant temp gauge is a dummy gauge like the oil pressure gauge.

it is not 100% fake but fakeish...   it is damped very heavily!

I haven't gotten the code back, but I would still like to check the thermostat.  Where can I find it and how would I be able to tell if it's stuck open?

I know Moss has the Long thermostat for sale w/ their SC kit.
as it seems the early 06 models had short thermostats,
and w/ the SC needed the Mazda Long thermostats, which were used late 06+
or atleast that is what I understood from reading amp; searching
not that it seems you are using a SC, but you may have the older short t-stat...hence your car is a 06.
my auterra database shows p0126 as
generic - insuffeicent coolant temp for stable operation
did it seem to lose any power or go into a safe mode?  just wondering
as for where; should be in the moss sc pdf instructions somewhere.
graphics/p...99-830_web.pdf
look at illustration #25 which is the thermostat housing

What Replay is trying to tell you is that the thermostat and housing are a unit (at least on the '06), and you don't get to buy the cheap replacement thermostat.  
Also, you'll find it really entertaining when you try to remove it -- I think you'll have to get the plastic part of the intake manifold off first.  These cars are not designed to be serviced.
jim

yea, what he said.   
looks like a pita.
I have no clue what im talking about,  just trying to point you in good direction.

It also could be the sensor itself that is giving false readings. I would top off the coolant, if needed, and see if the code comes back.

I had topped off the coolant with some FL-22 and cleared the code via a code reader.  The code has not come back (it's been about 1000 miles since then).
The car felt a little more sluggish when the car first threw the code, but I think that's b/c the rear brakes were also dragging.  I've fixed that since then, but it still feels like it's just a hair slower in accceleration than it used to be before it threw the code.


Originally Posted by lyrictenor1
I had topped off the coolant with some FL-22 and cleared the code via a code reader.  The code has not come back (it's been about 1000 miles since then)............

I reckon your car just quot;burpedquot; and now it will be OK..........
humfrz


Originally Posted by lyrictenor1
.... how would I be able to tell if it's stuck open?

If it#8217;s cool enough to handle and you can pour water through it, it#8217;s stuck open.
I remember watching my grandpa testing one he was hoping was stuck closed. He put it in a pot of water on grandma#8217;s stove and said if the water was boiling before it opened we were going to the auto parts store for a new one. A few moments later it opened. I don#8217;t remember what he was working on or what the problem was, just remember the thermostat opening in the soup pot.
I agree with Mr Humfrz, you most likely don#8217;t have a problem since the code never came back.

I got this code when I ran the car without the thermostat for a week.  All you need to do to get to the thermostat housing is remove the throttle body.  All in all a 30 minute job.

Well, it came back on...probably is a bad thermostat.
I had CEL P0126 (insufficient coolant temperature) last night-- my scangauge at the time the CEL came on said 159 degrees Farenheit. The car normally runs between 190-216F during the day in normal operation.
I had just been driving in the twisties and was behind a slower car, so I stopped running at higher revs and gave the engine a break. The temp had also cooled down a bit by that point in the evening, so if the thermostat is stuck open along with those other things going on I can see why the coolant temp dropped so much.
My apologies to those who read the other read by me: quot;Normal coolant operating temperaturequot; as the story is the same as in that thread.  I thought I'd mention in this thread the CEL came back.

Thanks for posting that the code came back.
how many miles do ya have on yer NC?

89k now. Problem first appeared at 85k.


Originally Posted by MXGeorge
I got this code when I ran the car without the thermostat for a week.  All you need to do to get to the thermostat housing is remove the throttle body.  All in all a 30 minute job.

Thanks for the tip, MXGeorge.  Do you (or anyone else here) have instructions on how to do this?  I plan to pick up a new thermostat this week and replace it myself.


Originally Posted by lyrictenor1
Thanks for the tip, MXGeorge.  Do you (or anyone else here) have instructions on how to do this?  I plan to pick up a new thermostat this week and replace it myself.

Instructions are as follows:
a.  Remove the throttle body and air inlet tube to get them out of the way.
b.  Squeeze the clamps on the 2 hoses going to the thermostat housing which is directly below the throttle body, and pull the clamps down the hoses.
c.  Pull the hoses off the thermostat hosing.
d.  Remove the 3 bolts holding the thermostat housing to the block.  
e.  Pull the housing off.
f.  Do everything in reverse to reinstal it.

Thanks, MXGeorge!  I'll give it a shot today.

MXGeorge,
I noticed when I removed the hoses a bunch of coolant came out.  When I'm putting this back together, I'm assuming I'm going to need to replace some of that coolant.  Are there any special procedures to refilling the coolant in this regard?  Can I just replace through the reservoir or do I need to quot;burpquot; the cooling system?  (I don't know how to do that btw)

You will notice that what happened is that your reservoir just got emptied.  Just bolt everything up and refill it with the car running.  Should be ok.  If you feel that there is air in there, unbolt the reservoir and raise it somewhat while tapping it.  Oh yeah, the cap should be off.