Hi Mr. Scotty, how are you? Respectfully, I have a 2018 GMC Acadia with codes: U0401 (invalid data received from ECM) and P0128 (engine coolant temperature below thermostat temperature). With codes on the cooling fan runs continuously, AC will not work and engine temperature sensor will not work. Once cleared, (the codes stays on but MIL disappeared) AC will work normal. Engine temperature sensor/gauge will work normal and cooling fan only kicks in as of when necessary. It takes roughly 2/3 weeks for the codes to be set again once cleared. Has been like that for at least 6-8 months. I am thinking of replacing the engine coolant sensor. What do you recommend please? Many thanks.
Hi Mr. Scotty, how are you? Respectfully, I have a 2018 GMC Acadia with codes: U0401 (invalid data received from ECM) and P0128 (engine coolant temperature below thermostat temperature). With codes on the cooling fan runs continuously, AC will not work and engine temperature sensor will not work. Once cleared, (the codes stays on but MIL disappeared) AC will work normal. Engine temperature sensor/gauge will work normal and cooling fan only kicks in as of when necessary. It takes roughly 2/3 weeks for the codes to be set again once cleared. Has been like that for at least 6-8 months. I am thinking of replacing the engine coolant sensor. What do you recommend please? Many thanks.
You can tell right away from a basic scan tool as to whether or not the engine coolant sensor is malfunctioning by looking at live data. It should read around 190 degrees Fahrenheit with the car fully warmed up. You can also look for clues to what's going on with freeze frame data when the AC stops working. Don't just guess that the coolant temperature sensor is bad.
