Variable Tuning Signal Circuit
WARNING: This page is about a different car, the 2006 Chevrolet Monte Carlo and 2006 Chevrolet Impala. However, it is still accessible from the selected car via links, so may be relevant.
During operation when the valve is open the control module applies ground to the variable tuning signal circuit which indicates to the microprocessor within the IMT valve to position the valve to the closed position which turns the motor ON and rotates the IMT valve within the intake manifold plenum.