Ice accumulation on exposed portion of LLCV needle valve needle not applicable to CP2's recent misbehaviour.  Instead, the pneumatic actuator box required thawing via the heat gun.  As found, the needle was stuck in it's nominal position (~15% open) and wouldn't stroke when >nominal open settings were selected (in manual control mode) or stroke closed with the instrument air valved out.  With the actuator thawed, now the needle strokes freely through 0-100% settings.  

CP1 is working at this time but was probably experiencing a similar problem yesterday.