2010 Prius - P0118

P0118 indicates an open somewhere in the circuit for that temperature sensor. Look for that.

Toyota Service Information and Where To Find It | PriusChat

 

An open in the electrical circuit that connects that temperature sensor to the engine control module.

In #2 above, I gave a link to the Toyota service information, where you can find the repair manual, wiring diagram, and troubleshooting steps.

If a term like "open" in an electrical circuit isn't familiar to you, there are probably a lot of options for you to pick up skills in that area:

auto electric diagnosis basics - Google Search

Also, if you sign in on TIS (described in the Toyota service info link), you have access to all the Toyota technician training modules, including the ones for training in electrical diagnosis skills.

 

Attached is relevant excerpt from (static, possibly dated) Repair Manual:

 

No.

The sensor used is a negative-temperature-coefficient thermistor. An open in the electrical circuit "looks" the same as a coolant temperature way down around −40°.

So you might be able to get a spurious P0118 on certain winter days in Alaska, but it's not likely in Philly in October, air pockets or no air pockets.

 

it is not normal

 

i can't say for sure, but it might be a short in the wiring, or corroded pins at the ecu, or an ecu problem

 

The code indicates an open in the sensor circuit. If the code is intermittent, the open is intermittent. Non-intermittent ones can be easier to find, but that's about the only difference.