2005 Prius Overheating light/ loss in power/ heater not working

1. DTC P0117 means that the engine ECU thinks the temperature in the cylinder head reached 140 degrees C (normal operating temp is 82 degrees C). That is a sign of severe overheating and if this actually happened, your engine probably is destroyed. (An alternative explanation is that the wiring harness to the temperature sensor shorted, but that seems unlikely given the circumstances.)

2. Check the coolant level in the radiator. You have to remove the large black plastic panel over the radiator for access to the radiator cap. I believe you will find the level is low. If the fluid level is very low, you probably have caused permanent damage to the engine.

3. Assuming the coolant is low, at this point you would need to determine why the coolant level is low, fix the problem (probably a leaking engine coolant pump, look for coolant stains on the inside of the coolant pump pulley and on the air conditioner compressor below the pump) , refill the coolant, get all air out of the engine coolant system, and see how the power train performs.

4. #3 is not a minor activity if you don't have prior experience working on auto coolant systems. I've posted on how to do this with the Prius which is more complex compared to a typical vehicle because of the engine coolant heat recovery system which also needs to be purged of air.

5. If the coolant system has air in it, that might explain P1121 which means that the engine coolant flow control valve has failed. and would also explain why the cabin heater is not functioning.

6. DTC P1116 means a problem with the temperature sensor at the coolant heat recovery system canister. That might be caused by a general overheating issue.

 

The car is likely killed by neglect. When the car tells you to stop driving, you do so and fix it. You made your choice, I don't think it was a good one.

 

Agreed. My diagnosis: woman driver.

 

A cheap shot and totally unhelpful comment.

 

Your two posts seem to contradict each other. Did you really check the coolant on the road?

 

Obviously you need to find the leak and fix the cooling system first up. Look for signs of dried pink coolant (usually a pink crusty residue) where the pulley wheel attaches to the water pump (behind the fan belt). That's a very common place to get leakage.

You've definitely overheated the engine quite badly, and no doubt some amount of damage has been done. If you're really lucky you just added about 100 to 200 thousand miles worth of wear on it and nothing else. But there may be more damage than that, for example a blown head gasket is not unlikely. Keep an eye on the oil an make sure it's not getting "milky". Similarly with the coolant once you get that fixed, make sure you're not getting any oil in the coolant. If you see either of those things then it will be a blown head gasket.

 

OP probably looked at the radiator overflow container, saw there was coolant within, and assumed that coolant level was not an issue. (That was a reasonable assumption to make, by the way, if you are not familiar with the Prius.)

Unfortunately if the Prius develops an engine coolant leak where air can enter the system, it is possible that the coolant level in the radiator will drop without sucking fluid out of the overflow container. Hence if an overheating warning is seen, it is necessary to check coolant level in the radiator.

It is too late now, but the OP had the option to stop her car either at the side of the road or no later than after reaching the nearest small town so she would not be alone in the summer heat, call her fiancé who was less than 100 miles ahead, and ask him to turn around to pick her up and help.

Here is my post about how to replace the engine coolant pump. Within that post is a link to my other post about how to replace engine coolant. Perhaps that will be of help to the OP:
How to replace engine coolant pump and thermostat | PriusChat

 

Thanks for the reply, at this point we can only hope that your engine will perform satisfactorily for you.

If you should find the cabin heater is still not working, that is a clue you still have air in the engine coolant system. If you hear air bubbling around in the cabin heater core that is further evidence that air is in the system.

In that case, make the Prius READY, leave the gear selector in P, set the cabin temp control to MAX HEAT, turn the fan on to the fastest speed, and floor the accelerator pedal to rev up the engine as fast as it will spin so that the coolant will circulate. Do this for ~10 minutes or until you can feel the cabin heater is working correctly.

Check the radiator fluid after the engine has cooled down and replenish as needed. Continue to check the fluid daily before the car is first driven. Maintain the practice of daily checks until you find the fluid level in the radiator remains at the very top of the neck, before you declare victory.

 

The woman driver shot is an asshat thing to say. Hope you like living alone and keep that subscription to Vaseline going.