# OBD code PO128 **URL:** \ **Category:** Maintenance/Repairs\ **Tags:** fusion, ford\ **Created:** [March 29, 2010, 10:26pm UTC](https://community.cartalk.com/t/obd-code-po128/46849 "2010-03-29T22:26:02Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![Jordanreim](https://avatars.discourse-cdn.com/v4/letter/j/da6949/32.png) [@Jordanreim](https://community.cartalk.com/u/Jordanreim)\ **Post date:** [March 29, 2010, 10:26pm UTC](https://community.cartalk.com/t/obd-code-po128/46849/1 "2010-03-29T22:26:02Z")
I have a 2006 ford fusion and the check engine light came on with the code p0128. It says its the coolant thermostat but it never has overheated and the heat still works. The fluid levels are fine and so i dont know what to do for sure. Please help. ---
**Author:** ![Tester](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/tester/32/15976_2.png) [@Tester](https://community.cartalk.com/u/Tester)\ **Post date:** [March 29, 2010, 11:02pm UTC](https://community.cartalk.com/t/obd-code-po128/46849/2 "2010-03-29T23:02:42Z")
The code indicates that coolant temperature hasn’t reached the anticipated level for the amount of air that’s entered the engine. A partially stuck open thermostat can cause this code. Tester ---
**Author:** ![Jordanreim](https://avatars.discourse-cdn.com/v4/letter/j/da6949/32.png) [@Jordanreim](https://community.cartalk.com/u/Jordanreim)\ **Post date:** [March 30, 2010, 6:32am UTC](https://community.cartalk.com/t/obd-code-po128/46849/3 "2010-03-30T06:32:28Z")
Is the only way to fix it to replace it? ---
**Author:** ![JoeMario](https://avatars.discourse-cdn.com/v4/letter/j/3bc359/32.png) [@JoeMario](https://community.cartalk.com/u/JoeMario)\ **Post date:** [March 30, 2010, 10:56am UTC](https://community.cartalk.com/t/obd-code-po128/46849/4 "2010-03-30T10:56:39Z")
The only way to fix a “stuck open” thermostat is to replace it. ---
**Author:** ![cigroller](https://avatars.discourse-cdn.com/v4/letter/c/c68b51/32.png) [@cigroller](https://community.cartalk.com/u/cigroller)\ **Post date:** [March 30, 2010, 11:06am UTC](https://community.cartalk.com/t/obd-code-po128/46849/5 "2010-03-30T11:06:31Z")
The coolant temperature sensor should also be checked. This is easy. A thermostat replacement is also easy, and sometimes done just as a matter of maintenance. ---
**Author:** ![pdl777](https://avatars.discourse-cdn.com/v4/letter/p/b9e5f3/32.png) [@pdl777](https://community.cartalk.com/u/pdl777)\ **Post date:** [May 9, 2010, 8:36pm UTC](https://community.cartalk.com/t/obd-code-po128/46849/6 "2010-05-09T20:36:03Z")
Jordanreim, I have the same vehicle and had the same check engine light and code response when I checked it out. My thermostat was opening prematurely, thus the engine was running a bit cooler than “normal operating temperture”. If you are in Arizona like I am, that’s not too much concern since it lets the engine run cooler but should be repaired because everything is computer controlled and it could affect the overall performance. If you are in a cold climate area, it should be addressed sooner than later. One thing that can happen if you dont address it is the backend of the engine can possibly develope rust which is not a good thing but this usually takes awhile. I actually ran that way (not changing the thermostat) for approx 1 year with no problems or engine rust but it should be repaired. I have since had mine repaired. With the 4 cyl engine, the thermostat is not a simple replacement procedure. You have to remove a couple items above it to get to it. I paid $810.00 but had the front wheel bearings replaced too, an oil change, a coolant flush with my thermostat replaced too. I was quoted $350.00 to do it by itself by my mechanic. Hope this helps.