P1121 one week after main water pump replaced

DTC P1121 does point to the engine coolant flow control valve having failed. The dealer tech's work on the two coolant pumps should not have negatively affected this valve. It's reasonable to think of the part replacement as part of the on-going price you pay for owning a highly complex vehicle.

 

The work they did involves the cooling loop that contains that valve. At the very least they should check for free whether or not the system was filled and bled properly. I don't believe in coincidence when it comes to mechanical problems on these cars.

 

I had a p1121 code just after a coolant change in my 2004. Adding more coolant to the ICE coolant loop cleared the problem. My guess it that the coolant acts as a lubricant for the valve so a low ICE coolant level can cause the valve to stick.

JeffD

 

I brought my 2005 Prius in for the free recall replacement of the water pump. 2 days later the warning light came on. I took it back and they identified it as the p1121 code. They topped off the coolant level and said it was probably a bubble in the system. No charge. They warned that if the light came back on, it would mean replacing the coolant control valve sensor at the cost of 100+ for part and 297. for labor. The light came back on the next day, then off, then on for a couple of days. They told me to bring it back and they would recheck the code before ordering the part. Same p1121 code. They wanted me to pay ahead for the part before they ordered it. I protested that this seems like a problem as a result of their recall work and it should all be free. The part came in yesterday and they are replacing it tomorrow but I will have to pay. They insist that it is not related. I really don't believe them and just lost faith in my dealership. Has anyone been told that it is related? I have 82000 miles on my car and had no problem with my cooling system before brining it in. Please reply!

 

First, there are two independent coolant loops. You had a free service on the Inverter coolant loop where they replaced the electric coolant pump. If you also had them replace the Internal Combustion Engine (ICE) Coolant or the mechanical coolant pump then they also worked on the ICE coolant loop which is where the suspect valve is located. These are completely independent systems.

Low ICE coolant can cause a p1121 code as the ICE coolant acts as a lubricant for that valve. Check the coolant level in the ICE loop and top it off if necessary. If you continue to get a p1121 code, you will need to replace the valve at your cost and only a dealer or an experienced independent hybrid repair station can do this job for you.

JeffD

 

I'm having exactly same problem right now. I can't remember if I got the CEL with p1121 before or after the recall job but it was very close.

My noob questions is how easy it is to check and add the ICE coolant and what kind?

 

See my post #22 here which explains how to drain and replace engine coolant:
http://priuschat.com/forums/gen-ii-...shooting/30813-changing-engine-coolant-3.html

Since you just want to check the level and add, you'll only be doing a small subset of this activity. You need to remove the plastic cover over the radiator for access to the radiator cap. Remove the cap and fill the radiator fully, then fill the overflow reservoir to the top mark engraved on the side of the reservoir.

 

My dealer decided that the recall work probably did trigger the problem. They did not charge me for the work after all.

 

I am also seeing the P1121 code come and go. It started about 2 months after the inverter coolant recall service.

 

Check your coolant level (expansion tank) and check for a leak in your engine water pump (pink splotches on top of the A/C compressor)

 

When it first happened, I checked the coolant and the reservoir had some, but it was just under the L. So I topped it off. The level hasnt changed after that.

Since then, the P1121 comes and goes. It usually comes on when I drive for more than 20 minutes at a time, then goes back off a few drives later.

 

Next thing to check is physical damage to connectors at the thermos, underneath the driver side headlight.