Code P0128

2004 TOYOTA HIGHLANDER
197,800 MILES • 3.3L • V6 • 4WD • AUTOMATIC
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JITHIN MATHEW
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I got this code while on the highway with the cruise control set at 60 MPH. The temperature gauge is staying at where it should be and I am getting heat inside the car and car is does not overheat or overcool. I checked the engine coolant level and it’s level one radiator and reservoir. I replaced the coolant temperature sensor and it was working until 1 week later. I will post the freeze frame data. It says the IAT is at 52 degrees Fahrenheit even though it was only 37 degrees outside.
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Feb 2, 2020 at 6:34 AM
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AL514
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  • 5,464 POSTS
Hello,

This code is for Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature). This means there is either a wiring issue with the coolant temperature sensor or the thermostat is partially sticking open, preventing the engine from getting up to full operating temperature. I would deal with the thermostat issue first and then see if you get any other codes after the fix.
Feb 2, 2020 at 9:10 AM