We report a null detection of $^{12}CO$ emission from a sub-condensation in a High Velocity Cloud (HVC). As a consequence of this, an upper limit of $n(H_2)frac{X(CO)}{DV/DR}{leq}2{ imes}10^{-5}$ was set. This implies that $^{12}CO$ abundance is deficient by at least a factor of 10 if the HVC is predominantly molecular, otherwise the CO abundance of the HVC might be normal.