Question about 2002 Mercury Mountaineer

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Shows trouble code PO125 coolant temp. to low. replaced change still shows same code after driving 35 miles.

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  • gerry bissi May 11, 2010

    does the upper radiator hose get hot when the thermostat opens.



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I would have the OBD II scanner clear the codes. Then if the code still pops up, I would have the coolant temperature sensor looked at.

Posted on Oct 07, 2009

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Check engine temp w/infared thermom. just behind the thermo.housing on the engine. If above 180+ then check you sender(sensor) on the engine

Posted on Oct 07, 2009

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Swap out That Temp Sensor

Posted on Oct 07, 2009

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1 Answer

How do I get rid of the po125 code on a mitsubishi montero sport 4wd?

Did you replace the thermostat. Low coolant temp means the T stat is stuck open.

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I hope you realize that the po125 DTC code does not necessarily mean that you have a problem with the cylinder head temperature [CHT] sensor or the Engine Coolant Temperature [ECT] sensor.

It only means that the coolant temperature is too low for closed loop operation.

Other issues that may trip a DTC po125,
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  • Low engine coolant level
  • Leaking or stuck open thermostat
I would clear the code and see if it comes back- since you won't experience any difference in engine operation anyway.

You'll need to perform a continuity test on the sensor, when the engine is cool and then again after warming up the engine.

Then you'll want to take voltage readings on the wire harness that goes from the ECT back to the GEM.
You may find that the wire harness from the sensor to the GEM may be shorting out.

However, I would think that, if anything, the thermostat would be the culprit and malfunction before a faulty sensor.

You'll find the sensor under the upper radiator hose where the thermostat housing is mounted on the engine block. It may be obscured by the alternator.

And if you don't mind my 2 cents worth of friendly advice, either purchase a Chilton or Haynes repair manual from your local auto parts store or online.

Good luck on your project.

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My 1998 pontiac firebird service engine light came on and my OBD11 scanner produced 2 trouble codes PO125 ( insufficient coolant temperature for closed loop fuel control.the 3800V6 engine over heating and...

service the engine.. change oil ,filter plugs etc

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Diagnose Buick 3800 Engine
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P0125 is the OBD-II generic code for the engine computer, or Engine Control Module (ECM), not detecting enough heat in the cooling system before the fuel management system can take control. The ECM has a predetermined value after you start your vehicle to expect a certain coolant temperature

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ecm runs the engine cooling fans

3800V6 engine over heating and heater produces cold air
try these

EGR vale not working
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water pump fins corroded
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heater control tap stuck
directional actuator flaps stuck

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Insufficient coolant temperature for closed loop fuel control, how to fix problem? It's code po125

A code P0125 may mean that one or more of the following has happened:
The simplest thing to do is to reset the code and see if it comes back.
If the code comes back, the problem is likely going to be the result of the above causes (faulty thermostat, faulty ECT sensor, or a low coolant level) theres your answer need more help just tell me

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Did you bleed the coolant system?This needs to be done,and it should be fine,but you will have to have the code erased too.

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Check engine code po125 - 97 GP 3.8 - heater blows cold as engine temp rises to redline, then kicks in HOT and engine temp drops to normal... REPEAT. Is this the code for coolant temp sensor? Where is it...

What your describing is either a sticking thermostat, a low coolant condition or a blown cylinder head gasket.The code is for coolant temp fault.Not always the temp sensor but it is located next to the thermostat housing.

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