Code No. C1620 AYC control abnormality: Function

WARNING: This page is about a different car, the 2008 Mitsubishi Lancer. However, it is still accessible from the selected car via links, so may be relevant.

The AWC-ECU controls the specified current of the coil for the hydraulic unit AYC proportioning valve solenoid, and activation command of the coil for the AYC direction valve (RH/LH) solenoid.
The hydraulic unit AYC proportioning valve and direction valve (RH/LH) solenoid control the hydraulic pressure to the AYC differential right/left clutch.