Radiator dashboard lights ON...what does it mean

The temp sensor is between the inverter coolant jug and the back of your cylinder head screwed right into the block out right into the head I'm sorry I believe it's the head I have to actually physically go look but it's right there with a plug on it that's your engine coolant temp sensor one of them then there's another one in the bottom of the radiator so I don't know which one they're calling for It doesn't say in the list I believe they can both be tested with a test meter x amount of ohms for what the real water temperature is so if it's water temperature is 100°, it's 1,000 ohms That's not accurate I'm just using that as an example I think the temp sensor in the head is predominantly for the engine running systems and the one in the bottom of the radiator is for the radiator portion of the system I'm not sure why there's two one's for the EFI portion and ones for the regular water portion I do believe so there should be two at the system tells you which one it is You're good If not I'm not sure exactly how you discern other than testing them with an ohm meter The specs are probably in the manual which I can crack open this afternoon and tell you what the specs are for the sensor at a given temperature I do believe

 

Engine coolant temperature sensor replacement - P0117 | PriusChat

 

Be very careful with that bogus interpretation. That's why it's much more important to post the actual code.

I'm going to go out on a limb and guess the code you had was P0117 ?

That code means the temperature reading coming from the coolant temp sensor was so high the ECM wondered if it might mean a sensor problem.

Sometimes it does mean a sensor problem. On the other hand, if coolant is going away, you have to also consider the possibility that the engine really was that hot and the sensor is just doing its job. Changing out the sensor for that would be shooting the messenger.

Whatever Autozone tool told you the code meant "Replace Engine Coolant Temperature Sensor" belongs in the trash bin.

 

The engine coolant temperature sensor is very reliable and rarely goes bad. Based on what you wrote in post #1, I would guess that the engine water pump is going bad and needs to be replaced. A Toyota OEM pump is the preferred replacement because a cheap aftermarket pump will only last about one year.

 

I'm not criticizing you if they didn't give you the code.

I will say, if there's another time you go to a shop to have codes read, you really ought to insist that they give you the codes.

A code is five characters, the first one is P, C, B, or U, the next one is 0, 1, 2, or 3, and the next can all be digits 0 through 9 or letters A through F.

Those are what can actually be looked up in the repair manual to learn what the car is trying to tell you about.

Some one-liner built in to Autozone's tool that purports to tell you what the code "means" is much less useful.

 

Post #2 has a good step by step approach to solving your issue.
Autozone's job is to sell you parts; They didn't give you an error code to prevent you from making your own judgement on this issue.
@Brian1954 and @ChapmanF are experts here and layout pretty good advice from a blind diagnostic of a car. I would take that over some auto parts store jockey anytime.

FWIW; I used to be an auto parts store jockey in high school......

 

I am definitely not an expert. I am just a Gen 3 owner who has read many threads on this forum over the last five years concerning engine overheating and problems with the electric water pumps on this generation Prius. I have a theory that some of the headgasket problems are caused by the water pump going bad and not being replaced quickly enough. I added a display to the top of the dash (thank you rjparker, for sharing your setup), which is connected to the OBD2 port to monitor the engine coolant temperature anytime I drive my car.

I agree with you that ChapmanF is an expert.

 

The pink stuff from Autozone will work fine.

I have been using that coolant and have no issues.

Also running an AISIN water pump with the Toyota logo grinded off and got it from Amazon.

You can either choose to save money or enjoy spending more for the same stuff.

 

How much money do you give to error sellers?
Understand that if you do not delve into these issues yourself, you will be extorted for any issue.
There are simple diagnostic devices that will save your wallet.
Look at this topic.
Gen2 OBD2 app review | PriusChat

 

Read post #25 again.

Replace the engine water pump!!

Come back and report if that fixed the overheating problem.

 

First and foremost - get an accurate diagnosis which often means a dealer or hybrid specific independent. Most general mechanics can be fooled by a hybrid. Certainly don't go in telling them to change this or that without proof. Otherwise you can easily spend a $1,000 on parts you did not need.

Any coolant loss, fast or slow is bad. I have seen cars go five years and not lose a drop of coolant.

On these cars if you don't see coolant around the reservoir it is 95% going out the exhaust but in small quantities at first.

As noted above, the two temperature sensors are reliable and easily checked by a mechanic. Autozone has to have the absolute worst help - at least around here.

I would not be surprised if it's not a hose or a water pump. You would see red coolant or stains on the ground or on the engine. If it was the engine water pump, clogged passages or bad thermostat you would see red stains on top of the reservoir and particularly on the body behind the reservoir pressure cap (straight arrow) after it relieved excessive pressure.



Once the engine warms up you should see flow inside of the reservoir created by an open thermostat and a working pump. It's an easy visual check (curved arrow). You need a good led flashlight pressed on the reservoir plastic to see the flow after warmup.

Get a good diagnosis.

 

You are on the path to a bad head gasket.