P0128 Code on 2011 with normal engine temp
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2nd Gear
Joined: Sep 2022
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P0128 Code on 2011 with normal engine temp
Hello,
First time poster. I have a 2011 Ford F150 4x4 with the 5.0. When the transmission is not warmed up to normal temp, the transmission will not downshift pulling a hill. If I move it to manual and downshift myself, it works fine. It will throw code P0128. The truck has 300K miles on it and have had no problems. Is this the coolant sensor, thermostat or a computer programming issue? Thanks in advance! Chris
First time poster. I have a 2011 Ford F150 4x4 with the 5.0. When the transmission is not warmed up to normal temp, the transmission will not downshift pulling a hill. If I move it to manual and downshift myself, it works fine. It will throw code P0128. The truck has 300K miles on it and have had no problems. Is this the coolant sensor, thermostat or a computer programming issue? Thanks in advance! Chris
Laughing Gas
Joined: Dec 2010
Posts: 1,200
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From: Timbuk3, MI
DooDahDiddy...
The most common cause for P0128 is the engine coolant thermostat is stuck open. A simple way to diagnose this is to feel the radiator hose and monitor how hot the temperature of the coolant is when it starts flowing through the radiator hose.
Also... When was the last time the transmission's fluid was maintained?
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2nd Gear
Joined: Sep 2022
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Thanks, I had a rebuilt tranny put in at 275K with new fluid and torque converter. The engine temperature is indicating normally. I was thinking it might be a coolant or transmission sensor since it doesn't do any of this once the transmission is at normal operating temperature. It will not shift down, bucks and acts like it is missing. If I manually shift down there is no problem. Thanks!
3rd Gear
Joined: Jun 2024
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Replace your thermostat
If your thermostat sticks open even momentarily you get that fault code and you have reset it. I'd take it as a canary in the coal mine and replace your thermostat. It's super easy on the 4.6L I replaced mine easily. Shouldn't be too different in the bigger V8s, just make sure you drain 1.5 - 2 gallons from the petcock valve before opening the thermostat housing.
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