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I have a 2017 Ford Focus Se [mileage](/topics-mileage-for...


I have a 2017 Ford Focus Se [mileage](/topics-mileage-ford/) 38,000.The check [engine](/topics-engine-ford/) light came on last month and car was running cold i stopped by parts store it came back code po128. took it to Firestone ...

I have a 2017 Ford Focus Se [mileage](/topics-mileage-ford/) 38,000.The check [engine](/topics-engine-ford/) light came on last month and car was running cold i stopped by parts store it came back code po128. took it to Firestone the replaced both [thermostats](/topics-thermostat-ford/). 2weeks later and im having the same issue car running cold check engine light on with same code. if i dont turn on ac or heater temp gauge runs normal but as soon as i turn on either heat or ac the temp gauge falls to cold Mechanic's Assistant: Does the light stay on, or does it blink? Stays on Mechanic's Assistant: Are you fixing your Focus yourself? What have you tried so far? I took it to a repair shop. they replaced both thermostats

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Automotive Expert
Hi! Welcome to JustAnswer. Thank you for contacting us for assistance with your vehicle. I'm Ron. I will be happy to assist you with your question. May I ask to whom I have the pleasure of speaking with today?

Brenda
Automotive Expert
Good morning Brenda. Nice to see you today! I'm sorry to hear you are having this problem. I know this can be frustrating. After the thermostat was replaced did it all work properly for those 2 weeks?

No it still ran cold i called the shop and they said the new thermostat run a few degrees colder then the origonal ones
Automotive Expert
Thank you for the clarification, Please give me one moment to type out some information for you. Sit tight one minute. I'll be right back!

k thank you
Automotive Expert
Thank you for holding Brenda, Anytime you replace the thermostat it should NOT run cooler then the original thermostat, the temps should in fact reach normal operating temp of right at 192 degrees, The code P0128 can be set due to any of the following concerns, with the thermostat being the most common providing the cooling system is properly filled with no trapped air. This to me sounds like the replacement thermostat is likely defective. I would return to the shop and have then check it as well as the [coolant](/topics-coolant-ford/) system for trapped air and while doing so, monitor the ECT sensor to verify it, in fact, working properly. If these things check out okay, then they should consider replacing the thermostat again with the OEM Ford Factory replacement. - Low engine coolant level - Leaking or stuck open thermostat - Damaged engine coolant temperature (ECT) sensor

thank you they are gonna replace both thermostats again to see if that helps. i asked about the sensor and they told me that the 1 thermostat they replace the sensor was in the housing and therefore was replaced when they changed it. coolant level should be good they said they replaced it.
Automotive Expert
Okay, Brenda, I would insist that they use OEM Ford parts this time if they did not the last time.

I'm just trying to figure out all possible things that it coud be that way i can tell them right then. im assuming they used the ford part bc they had to order 2 thermostats from the ford dealerive never seen a car run cold with the ac on before it would have anything to do with the computer would it the reason i ask is the shop said if replacing the thermostat didnt work then i wwould have to replace the computer or reset the computer im just trying to mske sure they arent messing with me
Automotive Expert
Okay, the common cause for this type of problem is usually either failing thermostats low coolant and or trapped air in the cooling system and or a bad ECT. If that was new then that not likely the cause. It's running cold most likely because the thermostat is not controlling the coolant flow.

K so if they say i need to get the computer reset or changed dont do that bc it has nothing to do with my problem or is the ECT the computer so sorry im confused and dont want to end up paying htem a fortune bc i have no cluehow do i know if there is trapped air in the system and is it something i can check bc they are waiting on ford to send them thermostats again and they are on back order
Automotive Expert
No, this is not going to be a computer problem and or a programming concern. The ECT (engine coolant temp) sensor simply reads the engine coolant temp and sends that information to the computer to control the cooling fans. The only way to know if there is trapped air in the cooling system is to make sure it's properly bled. On this engine, the best way to bleed it is to use a vacuum bleeder tool.

Thank you one more question is the ect located on the thermostat housing. Bc i asked about the sensor and they told me its replaced anytime you replace the thermostat and hosuingor is there more then one sensor since my car does have 2 thermostats
Automotive Expert
Yes, it is, see its location in this link. [https://www.dropbox.com/s/fa4weaqmhxcvcs6/ECT%20location%20JAn%2026.pdf?dl=0](https://www.dropbox.com/s/fa4weaqmhxcvcs6/ECT%20location%20JAn%2026.pdf?dl=0)

k thank you so much. I just want to make sure i know everything i can so i can question them. you have been a big help thank you so much
Automotive Expert
Yes, it is, see its location in this link. There is only one ECT sensor as well. [https://www.dropbox.com/s/fa4weaqmhxcvcs6/ECT%20location%20JAn%2026.pdf?dl=0](https://www.dropbox.com/s/fa4weaqmhxcvcs6/ECT%20location%20JAn%2026.pdf?dl=0)
Automotive Expert
You're very welcome, Brenda! Glad I could be of some help today! I hope everything works out well for you! If there are any additional questions on this issue that should arise, please feel free to reply and ask! Have a great day!

thank you and you have a blessed day also
Automotive Expert
Thank you!

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