Did you bench test the DCCV, when it was off the car?
0volts/12volts is used to trigger both solenoids to open or closed!
12volts, if you apply air pressure with a cupped hand on the water inlet, the air shouldn't come out of both outlets.
0volts = The air should come out of both outlets.
I had to use WD40 , clean, 12volts + mussle the solenoids to work again!
The DCCV is a Dual electronic contol solenoids for coolant, the pistons can get seized, and the DACT loses control.
Like a bad fuel injector, or spouse!
Just because you got a signal + sound doesn't mean that it's working.
Do a LS forum search tool ''DCCV'' ,not thread.
Goggle ''Troubleshoot LS DCCV''