Does P1121 (coolant flow control valve) error code have to be fixed?

I've gone nearly two years without replacing mine. Got the part but too busy (lazy) to put it in now. The only problem with not replacing it from what I can tell is that if something else triggers your engine light you won't be able to tell because it's already on.

 

I am wondering if Cali will let your car pass the yearly inspection with the check engine light lit. I know here in Texas it doesn't matter what the cause is for the light to be on. If there is a code or a code pending, no pass. Like Cali, here in Texas they plug into your ODB port.

I know I did not answer your question, just posted the above as "food for thought".

 

No pass in Cali

 

P1121 is an indication that the valve is not operating properly. This can be caused by a lack of coolant at the valve as the coolant acts as a lubricant for the valve. You should check if your ICE coolant is low and add some, it may free up the valve. If the symptom first showed up after a replacement of your coolant, there may be an air bubble so have the system bled to get air out of it.

I had the indication several years ago in my 2004 Prius. It was just after the dealer had drained and refilled my coolant (required at 100k miles and every 50k miles thereafter). Adding coolant cleared the problem and it never came back.

JeffD

 

I'm with Dino33ca. Bought the part and the coolant, just haven't felt the need to change it out yet. The light does go out typically, and usually comes on after a restart. I passed emissions okay in June, but the light probably wasn't on.

 

If you reset the code, you have to drive for several cycles to populate OBD2 memory or they will fail your car automatically. Some OBD2 readers will indicate when your car can pass the test after a reset.

JeffD

 

Mine has been on intermittently for a couple of months. I just ordered the part and coolant and I'm going to change it next week because the problem is not going away. I'm starting to assume the CEL is the P1121 code and that's like the boy who cried wolf.

 

I don't understand this statement.

1. Have you actually retrieved the DTC? If you retrieved P1121 then the engine has a problem. The problem could range from inadequate coolant level to a failed engine coolant valve. If the coolant level is the problem, this cannot be ignored unless you don't mind stressing the engine and risking permanent damage for no good reason. If the failed valve is the problem, then the cabin heater functionality may be impaired and/or the engine warmup may be slightly impaired. The car will not pass an emissions test while the CEL remains on and as previously stated, the car must perform correctly over a number of drive cycles before the engine ECU will indicate the car is ready for emissions testing.
2. If you did not confirm that P1121 is the logged DTC then this should be done.
3. The boy who cried wolf gave a false alarm. If the check engine light is on, there is a problem. The nature of the problem is defined by the logged DTC.

 

Thanks for your input, and please forgive the faulty analogy. It sounds like many Prius drivers ignore this problem (thus the nature of the OP). It sounds like a relatively minor problem for many.

From reading your other posts on this subject, I did confirm the coolant level in the radiator is OK. I now keep a DTC reader in the car and pull over and check every time the CEL comes on, once a week or so. I even showed my wife how to do it. My Mini-VCI does not show any other issues.

I've been checking the cabin heater function while the code is showing and the engine is warm, and it works normally--a lot of heat, fast. Do you know if the electric heaters could be providing that? I didn't think of that until now. I'll try checking the heater hoses next time. But I hope I'll have the new part in very soon and there won't be a next time..

 

When stuck, the engine coolant valve is probably in the position that allows coolant to flow to the cabin heater core since the cabin heater is working well. The PTC electric elements only produce ~600W of power which is 40% of a hair dryer, not much when the car's interior is at freezing temp.