Hello everyone! I have had my Prius for about 2 months now. All has been well until about a week ago. The engine light has been coming on and off. So we took it to have it scanned and it came back as P1121 (Coolant Flow Control). We took it to Nissan and had both coolant reservoirs topped off and the light cleared to see if that would help. But it is still coming on 90% of the time we take it out. How serious is this? Any fixes that I can try to do myself? It look like around 400 to have NIssan replace it . Thank you!
Its the coolant control valve. Very common Lots of posts about it on this site just search the P1121. Also the coolant reservoir may show full but the radiator itself may be very low. Take the black plastic cover off the top of the rad revealing the radiator cap. Take that off and check coolant level. Also the check engine light may be because the car is very very low on engine oil. A high mileage 2005 (never posted mileage) most likely will eat alot of engine oil. You should check it very closely every day until you get a handle on the oil loss. Run it real low just once and you can kill the motor. It takes 28 seconds to check the engine oil. Why would you take the car to a Nissan dealer?
Thank you for the response. How do I check the radiator level itself? Just by seeing if the fluid is at the top near the cap? If I don't see the fluid should I just slowly fill the radiator until it is topped off? Are you saying that the light could be on for low oil or are you just saying we should check that as well? I guess we could take to a local mechanic vs taking it to Nissas. I was just using them as a high estimate to fix the problem.
Yes should be at the top of the rad and yes just pour it in. Go to Toyota and buy a gallon of LLC Coolant. Yes could be low engine oil and yes I am saying its low for a reason its most likely eating oil if its high miles. These cars really don't leak oil they eat oil. You should watch it closely to see how bad its oil diet is. Unless you want to buy a new motor. Mileage is still a mystery.
150k on the motor. So you are right to assume. I will check radiator level and oil level tonight. I will make sure both are topped off. Then I will have the light reset. If it comes on again I guess it is the Coolant Flow Control. I guess my question is how serious of a problem is the Coolant Flow Control? Should be get it replaced before driving again or just as soon as possible?
No a lot of people font replace it for a long time. Use the search button on the top of the page and search that code lots of posts.
There's no problem driving with the p1121 error, just the check engine light. You should replace the valve at your convenience
Thank you. I am going to keep my eye on the coolant levels and get the code checked every few weeks until I have time to replace it to make sure there are no new codes. I heard the only downside to this valve is that it reduces heat to the cabin in the winter.
I have been driving with mine stuck for a while. It is the valve that directs hot coolant to the thermos (hot coolant reservoir) to help speed engine warm up. I'm in California so it doesn't do as much as in colder climates. Here is a link to repair description Prius P1121: Coolant Flow Control Valve Position Sensor Stuck - Luscious Garage | Hybrid Specialists iPhone ?
