P1116 Won’t Go Away

I have an '08 with this exact same problem and I haven't replaced anything upon close inspection so far everything seems to be spot-on I need to verify that the pump next to the coolant heat storage tank in fact runs I think it's supposed to come on at like 5 hours after a shutdown. I have not even bothered fooling with this much because it does not foul the car in any way I just cleared the code so my light isn't on and that's about it The coolant heat storage tank can't be bad unless it's been crushed in an accident or someone drilled a hole in it or something crazy It's just a tank You should be able to blow air through the in and out pots and what have you. And that's about it The temp sensor that screwed into the heat storage tank I'm sure there's some specifications I haven't found them yet to test it but generally speaking Toyota temp sensors are pretty stout and this one here is not measuring anything past 200° ever so it's not in a very serious application seemingly. My car has heat almost instantaneously end of the driveway warm air is coming out the vents coolant or spot on I've never replaced the water pump in a generation too maybe all of mine have already been done when I get the cars but it doesn't look like it looks like a standard old Corolla K engine water pump pretty long-lasting generally speaking. The only thing I can think of is the electronic control module that works all this is seeing something it doesn't like or is just gone crazy but I don't know this for a fact and I'm certainly not ripping this mint condition interior apart for something so silly I need to do the 5-hour test and see what that turns up and then that'll pinpoint it to the one of two things and I can't remember what they are right now but this is certainly a back burner item as everything else on this car is spot on and it's in the wind everyday so we just clear it when it happens and enjoy the car and in the summer time this doesn't happen that I do know I had the car in the hot weather just a few months ago.

 

Read the repair business in the paper manual or the online manual about this It's not very concise but there's a test you do about 5 hours after you shut the car down the car will come on I think and put that pump on then determine the temperature of that tank water and what it's looking for and by the end of that it points you to two things I can't remember what they are but I just really haven't had any time to spend on it everything is seemingly working so it seems to be something that is eProm or computer related some value is not being met for some reason but it's not because anything in the coolant path is compromised more likely the pump doesn't come on when it's supposed to to get the reading of what's in the tank versus whatever it's looking for and it's memory or what have you. This is one that's not going to affect you in any way other than the irritating light is on It can't hurt anything We have a water jacket around an exhaust pipe I don't think a prolonged warm up is even an issue in a Prius for that reason and for this coolant storage tank.

 

No it's not a fuse thing It is a computer like thing if you read the troubleshooting exactly for this problem in the manual it's long winded and there are two tests you're going to do and to do them you're going to have to pull the fender liner back on the driver side of the car where the wheel is so you can see feel and touch the pump and maybe check that temp sensor with an ohm meter I think the specs may be in the manual for that temp sensor and then you're going to drive the car heated up pull in and park it and read in the manual about what happens at 5 hours You want to be there a few minutes before the 5 hours is up and listening here if the pump comes on runs the cycle It pulls water out of that tank which is supposed to be a certain amount of degrees after 5 hours or some such nonsense and when the computer doesn't see the temperature it's looking for It will set this code upon startup that's exactly why you see it at startup and not while you're driving around because it has nothing to do with driving around. So it could be a computer problem and I think it helps you separate that in the workup for the coolant heat recovery tank and or system The tank has no bladder or anything in it to go bad it's just an aluminum tank and unless it's damaged by an accident they can't really rust away or anything like that because of the material that's made out of so replacing the tank seems like a nonsensical exercise unless you can physically see dense breaks cracks or holes in that pretty silver aluminum tank not likely. Or there's a problem with what's controlling all this I don't know if it's the body control module or what computer it is and I'm not about to tear up my gorgeous condition interior vents coming out and what have you possibly breaking to swap out a computer that's telling me something about the tank that holds hot water that has really no bearing on anything other than fast warm up to get the optimal temperature quickly other than that it has no effect pretty much on the car running other than the light on which for some people that can be like a letter from the president you know.

 

Nothing is harming the coolant system and as you see the car is running perfectly down the highway in town whatever this only has to do with what the temperature of that fluid in that tank is after so much time If it doesn't like what it sees would seem to me like a computer or E-Prom issue.

 

It sounds like everyone is guessing at what could be wrong and throwing parts at the problem.

My first step would be to have a capable scantool and look at what the Coolant Heat Storage system is doing on a cold start. The scantool has to be able to view Prius specific data from the ECM.

Normally, if you power on to ready mode (with the heater turned off), the CHS electric pump will run some 5+ seconds before the ICE starts up. The CHS (water outlet) temperature will go up followed by ECT (engine coolant temperature)

On my 06 during a cold start, Water outlet went from 42° to a peak of 150° while ECT went up to 140° but for slightly longer.
Then the ICE started up.

For setup, I went to ignition on (power button x2 but no foot on brake pedal). Turn off HVAC blower. Connect scantool and select the needed data. (If the scantool can record data then do so) Go ready and see what the car does.

If your scantool has bidirectional controls, it makes it easier as you can command the pump to run and see - hear - feel if it does.

Posted via the PriusChat mobile app.

 

Yes and per the manual like 5 hours after shutdown that fender mounted pump should run and then the coolant temperature is red by the sensor and if it's above or below a threshold it'll set the code for the light to come on when the car starts or something along those lines I read over it once so I need to shut the car off and it 4 hours and 40 minutes go out to the car and wait and see if the pump comes on somewhere around the 5-hour mark and then if that sets the code then it's I can't remember

 

It sounds like there's a bit of confusion going on with the OP about what the P1116 is signifying. CHST isn't my area of expertise, but here's my general understanding of it.

The coolant heat storage tank is located in the front driver fender. It has an electric pump mounted on the bottom and a temperature sensor mounted on the outlet. All it does is store coolant and keep it hot so when you get ready to start the car next time, it pumps that hot coolant into the engine to quicken the warmup time, to reduce emissions. Only the North American gen 2 prius has this.

Turn the engine off, the pump runs to move hot coolant into the tank. Restart the car later, and the pump runs to circulate the coolant to the engine. The car knows whether this works or not by using the temperature sensor. It looks at the change in temperature compared to engine temp to see if coolant moved. If inadequate temperature change, then either something is preventing flow, or the temp sensor is bad.

If flow is actually occurring, but no 'sensed' temp change then the problem lies in the sensor circuit.
What can prevent flow? The flow path has a blockage or the pump isn't running. We have seen hoses installed incorrectly at the tank and 3-way valve cause this problem. May also be caused by inadequate bleeding. Could it be caused by something as simple as a control relay with an intermittent failure? The CHST pump relay is located in the small relay box mounted just behind the engine above the valve cover. It would probably suck to have it end up being a $4 relay that was causing your 'problem'. Would be a cheap part to just replace and see what happens. Better than the $1000+ you've probably already spent.

In the big picture, that code and whatever is triggering it is going to have zero affect on how the car runs, other than your warmup time may be a minute or to longer.

 

Luckily so far we haven't spent the dime we've just been turning it off the light that is and that's what I figured either the pump or the temp sensor I'm gambling the pump because the temp sensor is generally pretty stout and Toyotas but maybe not anymore.

 

True enough.

However, the OP has had a bunch of things done "to see what happens". That's why I suggest getting some data to see what the system does or doesn't do right now.

This doesn't affect the car's function, but if you want or need the MIL to stay off then you gotta fix it.

Posted via the PriusChat mobile app.

 

Definitely agree with this. Data doesn't lie and inspectors and buyers hate warning lights.