P0128 is 99% of the time a stuck open thermostat as the code means that the engine isn't reaching the thermostat's control temperature. That would fit with the cool running aspect as well. On that engine the thermostat is serviced as part of the water outlet housing as shown. Drain the cooling system, disconnect the knock sensor connector, remove the heater hose and rad hose from the outlet, then remove the three bolts. Clean the surface up and reverse the process to install the new one. Try to get an OE part 3M4Z8575B as the aftermarket ones tend to leak.
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Sunday, February 26th, 2023 AT 1:08 PM