I recently purchased a 2018 Premium model with 102k miles and after driving about 300 miles it threw a P0128 code. Looking at the Carfax the thermostat and fan clutch were replaced around 4k miles ago. Cleared the code and went several hundred miles further and then threw the code again. Not sure where to start trying to troubleshoot this code. Is it possible a bad replacement thermostat was installed (this was done at a Toyota dealership FWIW)? I do not have any coolant crust or staining on the bottom of the engine and bell housing, nor can I see any on topside of engine with naked eye (not that I expect to). The P0128 means the coolant isn't heating up to operating temp fast enough for the computer to like. The operating temp on the dash gauge is consistently just under the halfway point all the time and has been at that temp both times the code has been thrown. Just checking to see if anyone else has dealt with a phantom P0128 code?
P0128 code (1 Viewer)
- Thread starter fireman660r
- Start date
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r2m
Richard
Do you have a ScanGauge or OBDII Bluetooth dongle for your phone to get real time, accurate temperatures?
Wonder if your thermostat is stuck open?
Wonder if your thermostat is stuck open?
- Thread starter
- #3
Update. I used a scanner and monitored coolant temp and coolant would not get above 163* after 45 minute highway drive. I am guessing thermostat is stuck open. Ordered a new thermostat and will replace next weekend. Carfax report say thermostat was replaced 4k miles ago at a Toyota dealership. Is it possible to get a faulty Thermostat from Toyota? I know its "possible", but likely, or more likely the repair was lied about?
It's very possible that they used an aftermarket thermostat. It could have a defective OE tstat but I spent 35 years mostly at Ford dealership service parts and Used car departments will sometimes use the cheapest option on a car. Used car departments usually have their own techs seperate of the main dealership and will employ the cheapest route possible.
