Coolant flow control valve/P1121 and a buzzing noise?

I was told the same thing by Prime Toyota. "Priusses are complicated and there might be other things causing the code" and "the diagnosis of the check engine light is free". So I got there, and turns out just the first hour of diagnosis is free, then there is a $120 charge. So (brace yourself) it WAS more than an hour! $120 to be told yes, it was the coolant flow control valve! And an estimate of $556. Yes, I am an idiot for not leaving when they said only the first hour is free.
Oh, as to diagnosing with an oil change? Their "complimentary multi-point inspection" (not requested by me) said I need new spark plugs (replaced elsewhere 20k miles ago), a new muffler (maybe, I do live in New England) and an alignment (elsewhere 7k miles ago). Huh.

 

There is no such thing as a "first hour is free" diagnostic at Toyota. Paying $120 for diagnostic would be standard practice, you didn't get ripped off. However I just don't know why they need to do it since you know what you want done.

Does $556 include a coolant change?

 

It took more than an hour for them to diagnose the CEL and to determine that the cause was what you told them? The clock must have started when you entered their parking lot and run until the service tech had his second cup of coffee.

I believe the entire exhaust system is stainless steel - unlikely to rust out.

 

No idea about any coolant change, as the quote did not give a breakdown into parts and labor, just the single price.

 

The diagnostic charge at dealerships is more like a guarantee that the correct thing is being repaired. It's not really an accurate labor charge. Otherwise, it's the customer's responsibility to make the correct diagnosis.

 

The dealer does not guarantee it's the right diagnosis. They just make an effort to make the right diagnosis, if it's wrong, oh well

 

I just replace my coolant control valve. Everything in place correctly. Vehicle heats up in cabin well. Here's the problem :

At start up i can hear a buzz coming from the valve like its (on) or at least being powered.

2nd : My engine check light is still on still reading p1121.

Coolant is full in overflow, coolant resevior, and radiator.

Possible problems or solutions ?