P0128 Thermostat Stuck Open

[StayinStock]

Morning guys, wondering if anyone could give me some advice on this one. Have a code PO128 Thermostat stuck open code. Its not coming up to operating temp so I assume that its either right or the sensors gone bad. Seems to still be blowing heat though so not real sure. I know the best thing to do would be to take it to dealer and let them figure it out but their saying they cant get me in for a week or so... if its simple enough id rather just do it myself. Any insight? Anyone had this issue before?

 

[Cdubya]

If it is the thermostat, people have installed 170* thermostats without much fuss. I too would probably DIY rather than wait for the dealer.

 

[StayinStock]

yeah I can see the housing, doesnt look to bad to get too but my main concern is how much of a pain are these things to burp/get the air out of?

 

[Cdubya]

Check out Unbroken's comments here:
https://www.explorerst.org/threads/new-170-degree-thermostat.938/

 

[Gsutavo]

I have the same code P0128 a month ago, it is low engine coolant temperature, I changed the thermostat to 170 degrees and the problem continued, they made a diagnosis and it showed problems with the ECT sensor, Ford has a bulletin where it recommends changing the sensor ECT and knock sensor and wiring harness

 

[Gsutavo]

Does anyone know the code or part number for the ECT sensor or coolant temperature sensor? Thank you

 

[StayinStock]

So oddly enough mine decided to fix itself before I had the chance... ordered a new sensor and thermostat from rock auto... keeping them on standby just incase. Heres the motorcraft part number for the sensor. More Information for MOTORCRAFT DY1446 (rockauto.com)

 

[Gsutavo]

Sorry for the delay, thank you very much for the information, I will ask

 

[ButterBawlZ]

Anyone find a solution to this? Having the same issue now where my car won’t get over 150 degrees.

 

[StayinStock]

Mine started doing again too, its sporadic though. I plan to try to do the thermostat and sensor this weekend, ill report my results.

 

[Gatorst1r]

I just installed the mishimoto 160° thermostat. About two days after I installed it I am now getting the same code and my car is not running temperature. Could it be that this car just can’t handle that thermostat or is it probably stuck open? I know I could just pop the hood take the box out and check it real quick but I don’t have the time, so just looking for some advice.

 

[EDWYER]

I just installed the mishimoto 160° thermostat.

They have a specific thermostat for the Explorer ST? I am not seeing it on their site.

 

[gkmunch]

I had P0128 show up last week, and in a tizzy I cleared it (in hindsight I should have left it so the dealer could just take care of it). Wondering if/when it will come back on.

My OBDII gauge shows coolant temps around 168-172 during my ~20mi round trips in 70-80 degree ambient air.

Curious what it ideally should be? (closer to 200+ probably?)

The temp gauge on the dash shows slightly below halfway (definitely above the blue cool zone), so without the code or OBDII gauge, I would assume its operating normally... and maybe it is?

 

[gkmunch]

Anybody able to comment on what coolant temps I should be seeing?

P0128 has not returned yet; still seeing temps ~170 in relatively short around-town trips.