Check engine light on - code P1121

Hi Moti,

The part number is 16670-21010, MSRP is $70 and you can buy it for $53 plus shipping here:
Champion ToyotaWorld

I've attached the TSB so you can see the approximate location of the valve. The Toyota repair manual doesn't say much about how to remove the valve. Note that it is important to pay attention to how the three hoses are hooked up to the valve, you don't want to put the wrong hose on the wrong spout...

I recommend that you completely drain the engine coolant and replace with fresh Toyota SLLC. You will need to purchase two gallons, and can find my tips on how to do that procedure here, see my posts #22 and #42:
http://priuschat.com/forums/gen-ii-...13-changing-engine-coolant-5.html#post1053658

If you decide to do this job, please post photos of the coolant flow control valve and surrounding area to help others who may take this on in the future. Thanks.

 

Hello my name is Joshua I just like to say THANK YOU to Mr. Wong. Your knowledge has helped me out considerably. Sincerely, Josh

 

I have a 2008 Prius with the P1121 code. Is this the same part number for the valve assy. 16670-21010?

 

It should be the same for all 2G North American Prius, but confirm that with your Toyota parts source.

 

I have a 2005 Prius with the P1121 code with no others. Intermittent CEL. I noticed no CEL this morning until I was sitting in traffic, then CEL illuminated. Radiator is full to top when cool, but coolant was slightly below the neck recently - added Toyota SSL. I've seen no indication of leakage.

I've read all the P1121 related threads. So, I take it that the Coolant Flow Control Valve has nothing to do with proper ICE coolant system operation, right? Reason I ask is b/c I noticed after normal ICE operating temp reached the large radiator hose leading to the thermostat housing is never hot like the other side radiator hose. Does this indicate the thermostat is stuck as well? Would that have any effect on the cause of P1121 or a completely separate issue?

Coolant was last replaced by tech 6 years and 59,000 miles ago with warranty water pump. So they say.

Patrick, has Champion Toyota world changed their name?

 

One hot and one cool(er) radiator hose is probably an indication that the radiator is doing what it's supposed to do--radiating heat out of the coolant. You're right, the P1121 code has nothing to do with the flow at the radiator.

 

1. The coolant flow control valve regulates the flow of coolant to the cabin heater core and the coolant heat recovery system canister. Failure of the valve does not negatively impact engine cooling but you may find the cabin heat is less than you expect.

2. If one radiator hose is hot while the other is cool then the engine thermostat and the radiator are both working OK.

3. "warranty water pump" probably is the inverter coolant pump which is totally unrelated to the engine coolant system.

4. Champion Toyota is now Autonation Toyota Gulf Freeway, Houston, TX. That is a reasonable parts source for web orders. I've recently started using parts.com which has great pricing but their parts catalog is not as good as the dedicated Toyota dealer parts websites.

 

Thanks for taking time to respond to these calls for help. You all have been so gracious with sharing knowledge and experience with fellow DIYers and folks who just want to understand how things work or what to expect for repairs. Chat on.

 

You are still on the original coolant for the inverter cooling loop.

Read post #11 and watch the video to see the light.
Fluids | PriusChat

 

Thanks exstudent for reminding me why I haven't allowed anybody to service my vehicles other than warranty work. As for the inverter coolant, I had changed that myself in 11/15 along with the electric inverter pump (which was also replaced once under warranty).

Patrick, the ICE water pump (16100-29157-83) was replaced under warranty as well. What are the chances they likely just topped off SSL coolant then as well?

Now for the benefit of others: after I bought the car from a private seller I thought I would have the coolant flushed and replaced by Toyota tech. Mind you it was December in IL so no DIY. A week later the water pump was wrecked, hence the replacement - no cost. I read something about never flush the coolant system. What say you?

 

Well, when the engine coolant pump is removed, at least 3 quarts of coolant will come out.

There is no need to "flush" the engine coolant system which implies the use of water for the flushing. Just drain the engine coolant, then refill.

If you were to flush with water, then some of that water will remain in the system. As you know, Toyota Super Long Life Coolant is already premixed with distilled water, so the net result is that your overall antifreeze % is going to drop below 50% depending upon how much flush water remains in the system.

 

Thanks Patrick.

Concerning P1121, has there been any thought as to what the issue is with the coolant control valve - is it electrical or a physical (sticking) valve due to corrosion? If it's not electrical, how about trying to clean it up internally? After all, it's not a pump. I realize $70-$80 bucks is not much for some people, but when it occurs regularly (with maintaining two old Pri), then for some people it adds up to budget stress. Tinker or replace?

 

I haven't had to deal w/ this issue and do not know what is involved with cleaning. If you are successful in that effort pls post about it and provide photos to enhance the community's knowledge.

 

When I got mine out, it appeared mechanically jammed. And even though I'm an inveterate tinkerer and a retired engineer and volunteer firefighter, I didn't even think about trying to take the thing apart. Firefighters and engineers both really like to take things apart.

One of the reasons I wouldn't mess with it is I wouldn't want to go through the labor of removing it again if the tinkering failed. It wouldn't be really horrible the second time, but it's just something I didn't want to do for the $75 the thing cost me.

 

[QUOTEWhen I got mine out, it appeared mechanically jammed.][/QUOTE]
Looking at pictures, it looks like a ball valve. Would it not move?

I doubt it comes apart. I thought to inspect it and try to free it up, but if there is no way to work the ball valve, then the point is mute.

BTW, I cracked opened my old inverter coolant pump and, though I may be oblivious to the engineering, for the life of me I don't see how it could throw a code from a mechanical standpoint. The rotating unit with the fins (moves freely) is magnetically charged to the piece to which it mounts. That is all there is to it. So maybe it lost some magnetic strength? Or are these codes thrown b/c something electrical goes haywire?

One thing is for sure, there is a large mark up on these little plastic parts. Fortunately, I can currently afford it, but I think of so many who can't. So, I ask these questions.

Thanks again.

 

The inverter has an overheating sensor. That sensor is electrical in design, as it contains a variable resistor whose resistance decreases as the temperature increases.

You do not see many posts about inverter coolant pump failure in the winter. The pumps can fail in any season, but a failure does not become obvious until the car is driven in relatively high ambient temperatures over longer distances.

 

I have this code reported on my 2008 touring edition Prius . On another board , found reference to this http://www.revbase.com/BBBMotor/TSb/DownloadPdf?id=177707 . The bulletin indicates that the repair would be under warranty for CA vehicles, manufactured before mine. I am not brave enough to do the repair myself , but it would be nice if this was covered by a warranty. I have about 55000 miles on the vehicle .

Thanks for the information, as I can now locate the part.

 

What's your definition of regularly?

Original 3-way valve triggered CEL Jan 2014, 121,454miles. Had the car since new BTW. I would say 7years, 121K miles of service is a very long time. Not replacing the valve would just make life miserable during winter, is one cost savings option. Just replace if you can't live w/o heat. Tinkering may be a short term solution, requiring you to have to redo all the work again.

This valve replacement is pennies compared to other higher priced, regularly occuring, maintenance items (ie tires).

 

I thought I would come back and say I got your point. But, I think you missed mine. It's in the parenthesis. I was writing not just about this part needing replaced, but a one after another here lately "(with maintaining two old Pri), then for some people it adds up". I'm a Prius fan, and don't get me wrong the "tranny" didn't need replaced like millions of Fords, but it's been costly (even though I do most the work). Yes, tires cost too much. If one drives a little more aggressive than granny the Gen I and Gen II seem to eat tires for breakfast. And the options are tires that kill your MPG or $90. LRR tires that last 20-30K miles. Got any recommendations for tires?

Ok, maybe I'm just missing my 98 Sienna. Owned it 11 years and nothing needed replaced except a 12v battery after 9 years (b/c I let it sit) and just regular maintenance items.